List of file formats (alphabetical)

This alphabetical list of filename extensions contains standard extensions associated with computer files.

Sym

Ext.	Description	Used by
###	Temporary file	program-dependent format
#24	Printer data file for 24 pin matrix printer	LocoScript
#IB	Printer data file	LocoScript
#nn	Part of file image	Long
#SC	Printer data file	LocoScript
#ST	Standard mode printer definitions	LocoScript
$$$	OS/2 archive file (i.e. archives.$$$, keys.$$$)	OS/2
$$$	Temporary file
$?	ZX Spectrum file in HOBETA format
$00	Pipe file	DOS
$DB	Temporary file	dBASE IV
$ED	Editor temporary file	MS C
$O1	Pipe file	DOS
$VM	Virtual manager temporary file	Windows 3.x
)2(	LHA archiver temporary file	LHA
??$	Backup file	P-CAD
??_	Microsoft packed file	Expand
?DK	Disk image	Loaddskf.exe
?UT	Nonpacked FTN mail (? - flavor)	FTN software
!ut	Unfinished µTorrent download	µTorrent
___	Adinf table	Adinf
EX_	Compressed executable file	Note: EX could be any first two characters in a file extension (e.g. BM_ for compressed bitmap (BMP), DL_ for compressed library, etc.) Files compressed using this method have been in use on Microsoft software CDs and floppies since around 1995.
?Q?	Squeeze for CP/M and MS-DOS
~$~	Temporary file	1st Reader
~??	Old Backup files (.MNU to .~MN)	Resource Workshop - Borland Delphi
~H	Cardfile heap	AZZ Cardfile
μ	Metrowerks Codewarrior project
Π	THINK C project
@@1, @@2, etc.	Hidownload temporary file	Hidownload

#

Ext.	Description	Used by
0	Compressed harddisk data	DoubleSpace
0B	Printer font with lineDraw extended character set	PageMaker
1337	Kiwi's RTCoD File Format	Se7ensins & Teh1337
001, 002, ...	Split parts of a single whole file	FFSJ, HJSplit, JJSplit, split (Unix) (when using numeric suffixes)
1	Fax	many
1	Roff/nroff/troff/groff source for manual page	cawf2.zip
123	Spreadsheet	Lotus 1-2-3 version 9 - Lotus 1-2-3 version 97
15U	Printer font with PI font set	PageMaker
1ST	Usually README.1ST text file
1TX	1toX Logipole file
2GR	286 Grabber File	Win
301	Fax	Super FAX 2000 - Fax-Mail 96
386	Intel 80386 processor driver	Windows 3.x
386	Windows virtual device driver	Win
3DMF	QuickDraw 3D Metafile	QuickDraw
3DS	3D Studio Graphics format	3D Studio
3DT	Database in which the meta-data of a 3D Topicscape is held	3D Topicscape
3DV	3-D wireframe graphics by Oscar Garcia	3dv wireframe viewer
3FX	Effect	CorelChart
3GA	Mobile Phone Audio (Samsung)
3GP	Mobile Phone Video
3GR	386 Grabber File	Win
3T4	Binary file converter to ASCII	Util3
4C$	Datafile	4Cast/2
4MD	Musical file
4SW	4DOS Swap File	4DOS
4TH	FORTH source code file	ForthCMP - LMI Forth
555	16 bit per pixel image file format (5bit per component)	Sierra Entertainment
602	Text (fairly simple format - plain text with binary control commands embedded within text lines and special formatting commands on dedicated lines)	Text602 text processor by Software602
668	Music (the mixing is always at 12048 Hz)
669	Music (8 channels)	The 669 Composer
6CM	Music (6 Channel Module)	Triton FastTracker
75	75×75 dpi display font	Ventura Publisher
7z	7-Zipped file
8	A86 assembler source code file
85	85×85 dpi display font	Ventura Publisher
8BF	Adobe Photoshop compatibile filters/plugins
890	ScanTitling subtitle files
8CM	Music (8 Channel Module)	Triton FastTracker
8M	Printer font with Math 8 extended character set	PageMaker
8U	Printer font with Roman 8 extended character set	PageMaker
83p	Executable program for TI-83 Plus Graphing Calculator	TI Connect
89p	Executable program for TI-89/89 Titanium Graphing Calculator	TI Connect
8xp	Executable program for TI-83/84 Plus Graphing Calculator	TI Connect
91	91×91 dpi display font	Ventura Publisher
96	96×96 dpi display font	Ventura Publisher

A

Ext.	Description	Used by
A	ADA source code file
A	Library	Unix
A##	AlZip Compressed Files' pieces
A11	Graphics AIIM image file
A80	Assembler language source for 8080
AA, AB, ...	Split parts of a single whole file	split (Unix)
AAC	Advanced Audio Coding is a standardized, lossy compression and encoding scheme for digital audio.
AAF	AutoPatcher file
AAF	Advanced Authoring Format is an advanced media wrapper file for professional applications.
AAS	Animation Play Script	AAPlay
AB6	Datafile	ABStat
AB8	Datafile	ABStat
ABC	Document	ABC FlowCharter 1.0
ABP	Data	ABComp compressed
ABP	AVS Barcode Profile	AVS Barcode Source
ABF	Adobe Binary Screen Font	Adobe Systems Software
ABK	Automatic backup file	CorelDRAW
ABM	Image PALS album file
ABM	Album file (various programs)
ABR	Adobe Brush file for PhotoShop	PhotoShop
ABS	Abstracts (info file)
ABS	Data file	Abscissa
AC	Project backup	Audit Command Language (ACL)
ACA	Project	Project Manager Workbench
ACB	Archive	ACB
ACB	see ACMB
ACC	Program (DR-DOS - ViewMax)	GEM / resident
ACCDA	Data	Microsoft Access Database Wizard (Open XML)
ACCDB	Data	Microsoft Access Database (Open XML)
ACCDE	Data	Microsoft Access Database Wizard (Open XML)
ACCDT	Data	Microsoft Access Database Template (Open XML)
ACCDU	Data	Microsoft Access Database Wizard (Open XML)
ACE	Archive	ACE
ACF	Adobe Custom Filter for PhotoShop	PhotoShop
ACL	Project	Audit Command Language (ACL)
ACL	AutoCorrect List	Microsoft Office
ACM	Audio Compression Module add-on	Win
ACMB	Graphics file
ACO	Adobe Color Palette
ACT	ACTOR source code file	ACTOR
ACT	Animations Works Actor (Graphics cell)	Animation Works
ACT	FoxDoc Action Diagrams	FoxPro
ACT	Presentation	Action!
AD	AfterDark screensaver module	AfterDark
AD2	ADPCM 2-bit compressed voice file	ZFAX
AD3	ADPCM 3-bit compressed voice file	ZFAX
ADA	Ada source code file
ADB	Ada Package Body
ADC	Bitmap graphics (16 colors)	Scanstudio
ADC	Dictionary	Lingvo
ADD	OS/2 adapter device driver
ADF	Amiga Disk File	unADF, UAE, WinUAE etc...
ADG	Data	ADG 3D Scene
ADI	Graphics file	AutoCAD
ADI	Database Index File	Advantage Database Server
ADICHT	LabChart data acquisition file	ADInstruments
ADL	MCA adapter description library	QEMM
ADM	After Dark support file	AfterDark
ADM	ADEM file format	ADEM
ADI	Database Memo File	Advantage Database Server
ADN	Add-in	Lotus 1-2-3
ADR	After Dark support file	AfterDark
ADS	Ada Package Specification
ADT	WoW geographical map location file	Blizzard Entertainment games (various)
ADT	Datafile for cardfile application	HP NewWave
ADT	Dictionary	Lingvo
ADT	Fax	AdTech
ADI	Database Table	Advantage Database Server
ADV	GUS device driver	Gf166.com
ADX	Document	Archetype Designer
ADZ	Amiga Disk Zipped (See Amiga Disk File)	GZip
AEP	After Effects Project File	Adobe After Effects
AF2	Flowchart	ABC FlowCharter 2.0
AF3	Flowchart	ABC FlowCharter 3.0
AFI	Truevision bitmap graphics
AFL	Font file (for Always)	Lotus 1-2-3
AFM	Datafile for cardfile application	HP NewWave
AFM	Type 1 font metric ASCII data for font installer	ATM - many
AFP	Shape palette	ABC FlowCharter
AFT	Template	ABC FlowCharter 3.0
AFW	Workplace	ABC FlowCharter 3.0
AGR	ArcView ASCII grid
AHK	AutoHotkey script file	AutoHotkey
AI	Vector graphics file	Adobe Illustrator
AIF	see AIFF
AIFC	Audio Interchange File Format with Compression
AIFF	Audio Interchange File Format	Convert (c) Villena
AiM	Asm Text Mode Image File	The Ultimate Draw
AIN	Archive	AIN
AIN	Job schedule	AutoIntern
AIO	APL programming language file transfer format file
AIR	Adobe AIR installation package	The Adobe AIR runtime environment.
AIS	Array of Intensity Samples graphics file	Xerox
AIX	Datafile for cardfile application	HP NewWave
AKM	"Akai Multitimbral" sample information file	Akai S5000 and S6000 hardware samplers (MS-DOS-based) and compatible software samplers
AKP	"Akai Program" sample information file	Akai S5000 and S6000 hardware samplers (MS-DOS-based) and compatible software samplers
ALC	Molecular coordinates	Alchemy, RasMol
ALG	Activity Log	ARCSOLO
ALE	Avid Log Exchange (used in film & video editing)	Avid
ALL	Arts & Letters symbol and font files	Arts & Letters
ALL	Filelist w/ all files	FRQView
ALL	Format file for working pages	Always
ALL	General printer information	WordPerfect for Win
ALO	Almanac support file
ALT	Menu file	WordPerfect Library
ALZ	AlZip Compressed Files
AMD	Maxum chromatograph offline database	Siemens Maxum Chromatograph
AMF	Music (Advanced Module Format)	DMP
AMG	Archive	AMGC
AMG	System image file	ACTOR
AML	AutomationML	AutomationML Group
AMR	Audio format for mobile phones (Nokia, SonyEricsson)
AMS	Adobe Monitor Setup calibration file	PhotoShop
AMS	Music format
ANI	Animation cursors for Win	Win95 - WinNT
ANI	Animation	IconAuthor
ANM	Animation	Deluxe Paint Animator
ANN	Help Annotations	Windows 3.x
Ann	Multi volume ARJ archive	ARJ
ANS	ANSI character graphics (animation) file	ANSView
ANS	ASCII text ANSI character set	NewWave Write
AOL	America On-line for Windows DLL	Win
AOS	Add-On Software	Nokia 9000
AP	Archive	WHAP
AP	Datafile	Datalex EntryPoint 90
APC	Printer driver	Lotus 1-2-3
APD	Printer driver	Lotus 1-2-3
APE	Monkey's Audio (Lossless)	audio media players
APF	Printer driver	Lotus 1-2-3
API	Adobe Printer Ink file for PhotoShop	PhotoShop
API	Passed parameter file	1st Reader
API	Printer driver	Lotus 1-2-3
APL	APL work space format file
APL	Support module used by Manugraphics APL products
APL	EV-Dos Application File
APM	Authorware Macintosh	Authorware
APP	Add-in application file	Symphony
APP	Application object file	dBASE Application Generator
APP	Application	FoxPro
APP	Application and Application Bundle	Mac OS X
APP	Executable workflow / macro file	Automator
APP	Executable application file	DR-DOS - NeXTstep - Atari
APP	Generated application	FoxPro
APR	Employee performance review	Employee Appraiser
APW	Authorware Windows	Authorware
APX	Appexpert database file	Borland C++ 4.5
AR	Argon - for 3D Modeling	Ashlar-Vellum
AR7	Archive	AR7
ARC	Archive	ARC - PKARC/PKXARC - PKPAS - PKUNPAK - QUARK
ARC	Archive	SQUASH
ARC	Nintendo proprietary archive format	Various Nintendo games
ARD	Map	Holux - Alan
ARF	Automatic Response File
ARH	Archivers definitions file	DN
ARI	Archive	ARI
ARJ	Archive	ARJ - ARJZ
ARK	ARC archive	CP/M port of ARC file archiver
ARK	Archive	QUARK
ARK	Managing your Money Archive File
ARR	Arrangement	Atari Cubase
ART	Gerber artwork	Cadence Allegro
ART	First Publisher, Designworks, Greenstreet Draw graphic file	All GST/Greenstreet Draw products
ART	Graphics (scrapbook)	Art Import
ART	Graphics format (Another Ray Tracer)	PFS:1st publisher - Art Import
ARTX	file format	Artisteer
ARTX	file format	belightsoft Text Art
ARX	Archive	ARX
ASC	ASCII text file
ASC	Transport armor file	PGP
ASD	Autosave file	Microsoft Word
ASD	Presentation	Astound
ASD	Screen driver	Lotus 1-2-3
ASD	Spectral Data Set	ASD Inc. RS3 spectral acquisition program
ASE	Velvet Studio Sample	AWAVE
ASE	ASCII Scene Export	3D Studio
ASF	Datafile	STATGRAPHICS
ASF	Screen font	Lotus 1-2-3
ASF	Advanced Streaming Format (Compressed Windows audio/video)	Microsoft Corporation
ASK	SYSGEN answer file	RT-11
ASH	Assembly language header file	TASM 3.0
ASI	ASIC language source	ASIC
ASI	Assembler include file	Turbo C - Borland C++
ASM	Assembler language source	TASM, MASM, NASM, Yasm, FASM
ASMX	ASP.NET Web Service	Microsoft Corporation
ASO	Assembler object (object-oriented) file	Turbo Assembler
ASP	ASPECT source code file	Procomm Plus
ASP	Association of Shareware Professionals OMBUDSMN.ASP notice
ASP	Active Server Pages of Microsoft.Net	Microsoft Corporation
ASPX	ActiveX Server Pages of Microsoft.Net	Microsoft Corporation
ASS	Amalgam Scene Specification	Halo 2 Map Editor
ASS	Advanced SubStation Alpha (Subtitles)
AST	Adobe Color Separation table for PhotoShop	PhotoShop
AST	Nintendo proprietary music streaming format	Various Nintendo games
ASV	Autosave File	MATLAB
ASW	Authorware Star	Authorware
ASX	Advanced Stream Redirector file, redirects to an ASF file (see ASF)	Microsoft Corporation
ASZ	Skin	AltDesk
AT2	Auto template	Aldus Persuasion 2.0
AT3	Atrac 3 Sound/music file	All Sony devices and programs with the Atrac 3+ specification
ATM	Adobe Type Manager data/info
ATN	Adobe Photoshop action	Adobe Photoshop
ATT	AT&T Group	GCGW
ATY	Produced when an association type is exported by 3D Topicscape	3D Topicscape
AU	Sun/NeXT/DEC Audio file	AWAVE, GoldWave
AU	Sound (audio) file	Sun Microsystems - Convert (c) Villena
AUD	Audio file	AudioRack
AUP	Audacity project file	Audacity
AUX	Auxiliary dictionary	ChiWriter
AUX	Auxiliary references	TeX/LaTeX
AUZ	Ableton Live File	Authorization File for Ableton Live
AVA	Publication	Avagio
AVB	AntiViral Toolkit Pro Bases
AVI	Audio Video Interleaved animation file	Video for Windows
AVR	Audio Visual Research	AWAVE
AVS	Audio Video Software	AVS Video Editor (video editing software)
AVT	AVATAR-coding files	A3E
AW	Text file	HP AdvanceWrite
AWA	Animations Works Accelerated Movie	Animation Works
AWD	Microsoft Fax At Work Document	Microsoft Fax At Work
AWK	AWK script/program
AWM	Animations Works Movie (as .AVI)	Animation Works
AWS	Data	STATGRAPHICS
Ax	Directshow filter file format
AXF	ARM Executable Image generated by the ARM tools.
AXM	Axmedis object	Axmedis Tools
AZD	Amazon Software Download	Amazon Software Download
AZW	DRM enabled eBook	All models of Amazon Kindle
AZW1	DRM enabled eBook with embedded fonts	All models Amazon Kindle
AZW2	Program file	All models of Amazon Kindle excluding Kindle 1
AZZ	Data file	AZZ Cardfile

B

Ext.	Description	Used by
B&W	Black and white graphics file	atari - mac
B&W	Mono binary screen image	1st Reader
B	Batch list	APPLAUSE
B	Grand Theft Auto saved game	Any of the 3D Grand Theft Auto games in either III or IV era.
B_W	Black and white graphics file	Atari - mac
B1N	Both mono and color binary screen image	1st Reader
B30	Printer font (JLaser - Cordata)	Corel Ventura Publisher
B3D	Blitz3D files
B8	Raw graphics file (one byte per pixel) plane two	PicLab
BA	Binary Archive	Scifer Archiver and Compression [External Header Mode]
BAC	Compiled BASIC	RT-11 BASIC-11
BAD	Bad file	Oracle Corporation - many
BAD	Animation file	Novalogic
BAD	File which covers bad blocks on disk volume (not to be moved)	RT-11
BAK	Backup file
BAL	Music score	Ballade
BALANCE	Balance accounting sheet file	Balance
BAP	Blaze Audio Wave Information File	BlazeAudio MadCap Software
BAR	Horizontal bar menu object file	dBASE Application Generator
BAR	Info Bar for GFX2EXE	GFX2EXE
BAR	Broker Archive. Compressed file containing number of other files for deployment.	IBM WebSphere Message Broker
BAS	BASIC language source	QuickBASIC - GW-BASIC - FreeBASIC
BAT	Batch file	MS-DOS, RT-11
BB	Database backup	Papyrus Design Group
BBL	Bibliographic reference file	TeX/BibTeX
BBM	Brush	Deluxe Paint
BBP	Playlist	BassBox
BBQ	BitBeamer Transfer Queue file	BitBeamer
BBS	Bulletin Board System announce or text info file
BBS	Hudson-style messagebase	FTN software
BC!	Unfinished download	Unfinished BitComet download (a BitTorrent client)
BCF	Card data	Bingo Card Creator
BCH	Batch process object file	dBASE Application Generator
BCH	Datafile	Datalex EntryPoint 90
BCO	Outline font description	Bitstream Inc.
BCP	Borland C++ makefile
BCT	Backup dictionary	Clarion
BCW	Environment settings	Borland C++ 4.5
BDB	Bookends database	Bookends
BDC	Dictionary	Lingvo
BDEF	Builder Definition	Websphere Portlet Factory
BDF	Adobe Glyph Bitmap Distribution Format	Adobe Software
BDF	Binary update file	BUPDATE.EXE (c) TNT Techn.
BDF	Bitmap Distribution Format font file	X11
BDF	Datafile	Egret
BDM	Videoclip	AVCHD
BDMV	Blu-ray Video Data Content file	Media players / software that supports Blu-ray structure
BDR	Border	Microsoft Publisher
BDT	Dictionary	Lingvo
BEF	Bleck Encrypted File
BEZ	Outline font description	Bitstream
BF	Brainfuck sourcefile
BF2	Bradford 2 font
BFC	Briefcase Win95	Win95
BFM	Font metrics	unix/Frame
BFX	Fax	BitFax
BGA	Bitmap graphics
BGI	Borland Graphics Interface device driver	Turbo C - Turbo Pascal
BH	Blackhole	data compression format
BI	BASIC include file	Visual Basic - FreeBASIC
BIB	Bibliography (ASCII)
BIB	Database - not compatible with TeX format	Papyrus
BIB	Literature database	TeX/BibTeX
BIF	Binary Image Format b&w graphics file	Image Capture board
BIK	Bink video file (RAD Video)
BIN	Binary file, usually zero-start (.com analog)
BIN	SGI Powerflip
BIN	Text mode memory dump	The Draw - TUD - ACiDDraw - etc.
BIO	BioniX Wallpaper playlist file	BioniX Wallpaper Changer
BIO	OS/2 BIOS
BIT	Bitmap X11
BK!	Document backup	WordPerfect for Win
BK	Faxbook	JetFax
BK?	Backup file
BKC	Backup catalog	Backup4all
BKn	Timed backup file for document window n	WordPerfect for Win
BKP	Backup file	Write - TurboVidion DialogDesigner
BKW	Mirror image of font set	FontEdit
BLD	BLoaDable picture	BASIC
BLD	SYSGEN Build procedure file	RT-11
BLEND	Blender3D Project File	Blender
BLG	Backup Log	ARCSOLO
BLK	Temporary file	WordPerfect for Win
BLOB	Unknown	Steam (software) for Win
BLP	Blizzard Game Picture	Blizzard Entertainment games (various)
BM	BitMap graphics file
BM3	UIQ3 Phone backup
BMD	Nintendo proprietary 3D model file	Various Nintendo games
BMK	Help Bookmarks	Windows 3.x
BMP	OS/2 or Win graphics format (BitMap Picture)	QPeg - CorelDraw - PC Paintbrush - many
BMPW	bitmap world-file - geo-references info
BMS	Nintendo proprietary MIDI tracker format	Various Nintendo games
BMT	Ami Pro Button	Ami Pro
BNA	Data	Atlas Boundary
BNK	Adlib instrument bank file
BNR	Graphics Banner	Banner - Poster
BOK	Shamela Library book	Shamela Library Program
BOO	Book-format	READIBM
BOO	Compressed file ASCII archive created by BOO (msbooasm.arc)	msbooasm.arc
BOO	Boo programming language source file.	Boo Programming Language
BOT	Bot files, these go with JKB files	Quake 3 Engine
BPC	Chart	Business Plan Toolkit
BPOLY	Data	Prisms binary 3D object
BPP	Backup application	Clarion
BPT	Bitmap fills file	CorelDRAW
BR	Script	Bridge
BRD	Eagle Layout File
BRD	Tanzzle board file	Tanzzle
BRD	Cadence Allegro board file	Cadence
BRF	Braille	Braille embossers and refreshable displays
BRK	Fax	Brooktrout Fax-Mail
BRK	The Brake! Mailer REXX script	The Brake!
BRL	CAD	Ballistic Research Laboratory CAD
BS2	Archive	BS2.EXE
BSA	Archive	BSArc
BSC	Compressed Apple II file archive created by BINSCII	BINSCII
BSC	Database	Source Browser
BSC	Pwbrmake object file	Microsoft Fortran
BSP	Half-Life\Half-Life 2 map files	Valve Corporation
BSS	Casio Phone base	PC-LINK
BST	BiblioTex file (BiblioTex=bibliography file)	TeX
BSY	Busy flag	FTN soft
BTM	Batch-to-memory (quick batch)	4dos -ndos
BTN	Makeover Button file
BUFR	Binary Universal Form for the Representation of Meteorological Data
BUG	Bugs and Problems
BUN	LucasArts Bundle File
BUP	Backup file
BUT	Button definitions	Buttons!
BUY	Datafile format	movie
BVn	Overflow file below insert point in Doc n	WordPerfect for Win
BWB	Spreadsheet application	Visual Baler
BWR	Beware (buglist)	Kermit
BYU	BYU Movie	BYU
BZ2	Archive	bzip2
BZM	Map	Blitzkrieg

C

Ext.	Description	Used by
C--	C—language source	Sphinx C--
C	C language source Note that on case sensitive platforms like Unix and with the gcc compiler the uppercase .C extension indicates a C++ source file.	Watcom C/C++, Borland C/C++, gcc and other C compilers
C	Unix file archive	COMPACT
C++	C++ language source
C00	Print file	Ventura Publisher
C01	Typhoon wave files	AWAVE
C86	C source code file	Computer Innovation C86
CA	Initial cache data for root domain servers	Telnet
CA?	Borland packed and split file	Borland Installer
CAB	Win 95 packed file	Win 95
CAC	dBASE IV executable when caching on/off (see cachedb.bat)
CAD	Drawing	BobCAD-CAM
CAD	Document	Drafix Windows CAD
CAL	Calendar file	Windows 3.x
CAL	Spreadsheet format	SuperCalc
CALS	Computer Aided Acquisition and Logistics
CALS	Support Raster Format
CAM	Casio Camera
CAN	Fax	Navigator Fax
CAP	Caption	Ventura Publisher
CAP	Capture file	ProComm - Telix
CAS	C + ASM language source	Turbo C
CAT	Catalog	CP Backup - dBASE IV
CAT	Device driver digital signature	Microsoft Windows
CAT	Stellarium Star Catalogue	Stellarium
CATDrawing	Drawing file of CATIA V5	CATIA V5
CATPart	Part file of CATIA V5	CATIA V5
CATProduct	Assembly file of CATIA V5	CATIA V5
CATS	Combined source	ATS
CBA	Source code	Creative BASIC
CBC	Fuzzy logic system	CubiCalc
CBL	COBOL source code file
CBM	Compiled bitmap graphics	XLib
CBR	Comic Book Reader (RAR file)	CDisplay and similar
CBS	MasterWord button bar configuration file
CBT	Computer Based Training	many
CBZ	Comic Book Reader (ZIP file)	CDisplay and similar
CC	C++ source code file
CC	CC language source	CC
CCC	Bitmap graphics (native format)	Curtain Call
CCF	Communications configuration file	Symphony
CCF	Color Chat file	Color Chat File
CCH	Chart	CorelChart
CCITT	CCITT Group 3 and Group 4 Encoding
CCL	Communication Command Language file	Intalk
CCO	BTX Graphics file	XBTX
CCT	Print Template	BobCAD-CAM
CD	CD description	DN
CDA	CD-Audio	Win95
CDB	Card database	CardScan
CDB	Main database	TCU Turbo C Utilities
CDF	Common Data Format
CDF	Company Data File	Nominal Small Business Accounting software
CDF	Computable Document Format	Mathematica
CDF	Cyberspace Description Format
CDF	Graphics	netcdf
CDK	Document	Atari Calamus
CDL	CADKey CADL Language	CADKey
CDM	Disk Drivers NPA	Novell NetWare
CDM	Music format (compressed)
CDR	Vector graphics format (drawing)	CorelDraw!
CDT	Corel Draw Template File	CorelDraw!
CDX	Compound index file	Visual FoxPro, Advantage Database Server
CE	Computer Eyes	Conversion Artist
CE	Main.ce	The FarSide Computer Calendar
CEB	Cont. Edge Bitmap	Conversion Artist
CEF	CA-Clipper Workbench Application	CA Clipper
CEF	Export File
CEF	Compact Embedded Font	Adobe Illustrator
CEG	Bitmap graphics	Tempra Show - Edsun Continuous Edge Graphics
CEL	Animation CEL	3D Studio
CEL	Graphics	Autodesk Animator - Lumena
CF	Configuration file	imake
CFA	Audio file	Adobe Premiere Pro
CFC	ColdFusion Component	Adobe ColdFusion
CFG	Configuration file
CFL	Chart	CorelFLOW
CFM	ColdFusion Markup Language	Adobe ColdFusion
CFN	Font data	Atari Calamus
CFO	C Form Object internal format object file	TCU Turbo C Utilities
CFP	Fax	The Complete Fax Portable
CFT	CFast graphics file	Disney Animation Studio
CGA	CGA display font	Ventura Publisher
CGI	Common Gateway Interface script
CGM	Computer Graphics Metafile vector graphics	A&L - HG - many
CH	Clipper language header	CA Clipper
CH3	Chart	Harvard Graphics 3.0
CH4	Presentation	Charisma 4.0
CHD	Font descriptor	FontChameleon
CHI	ChiWriter Document	ChiWriter - Chiview
CHK	Recovered data	DOS CHKDSK
CHK	Temporary file	WordPerfect for Win
CHL	Configuration History Log
CHM	Compiled Help File	Microsoft Windows, Help Explorer Viewer
CHML	Encrypted Data File	Krasbit Technologies, Chameleon Imaging Workflow Software
CHN	Data	Ethnograph 3
CHP	Chapter file	Ventura Publisher
CHR	Character set	Turbo C - Turbo Pascal
CHT	Chart	Harvard Graphics 2.0 - SoftCraft Presenter
CHT	CHeaT in any program/game	many
CHT	Interface file for ChartMaster	dBASE
CHZ	Archive	CHARC
CIF	Caltech Intermediate Format graphics file
CIF	Chapter information	Ventura Publisher
CIF	Crystallographic Information File	RasMol, Jmol
CiM	C Text Mode Image File	The Ultimate Draw
CIX	Database index	TCU Turbo C Utilities
CKB	Borland C++ 4.x editor keystroke mapping	BCW.EXE
CL	COMMON LISP source code file
CLA	Source	Clarion
CLASS	Java class file	Java
CLD	Clipper debugger configuration file	CA Clipper
CLJ	Clojure source code	Clojure
CLP	Clip art graphics file	Quattro Pro
CLP	Clipboard file	Windows 3.x
CLP	Compiler response file	CA Clipper
CLP	Graphics format	PCPAINT/Pictor
CLPI	ClipAV Clip Information file for Blu-ray	Media hardware / software with Blu-ray structure support
CLPRJ	ClassicLadder project file	ClassicLadder
CLR	Color binary screen image	1st Reader
CLR	Color definitions	Photostyler
CLR	Color scheme	Boxer/2
CLR	Palette file for GIS format
CLS	C++ class definition file
CLW	MFC Class Wizard information	Microsoft VC++
CM	Data file	CraftMan
CMB	Xtree for Windows Button Bar file
CMD	Command	dBASE - Waffle
CMD	Command Prompt batch file	Microsoft Windows NT based operating systems
CMD	executable programs	CP/M-86 operating system
CMD	External command menu	1st Reader
CMD	OS/2 batch/REXX file	OS/2
CMF	FM-music file (Creative Music File)
CMK	Card	Card Shop Plus
CMM	CMM script (batch) file	CEnvi
CMP	Bitmap graphics (Lead CMP compression)
CMP	Compressed data	PKWare Inc. data compression library
CMP	Header file for PostScript printer files	CorelDRAW
CMP	Photofinish Calibration Map	Photofinish
CMP	User dictionary	Microsoft Word for DOS
CMRL	Concise message routing language	DOTGO
CMS	Content Management System	Any Web Browser
CMU	Carnegie Mellon University Formats
CMV	Animation (CorelMove CorelDraw 4.0)	CorelMove CorelDraw 4.0
CNC	CNC general program data
CND	System generation conditional file	RT-11
CNF	Configuration (program - printer setup)	program - printer setup
CNF	Configuration file
CNV	Temporary file	WordPerfect for Win
CNV	Winword DLL used as part of an import operation (CNV=converter)	Microsoft Word
CO	Cobalt - parametric drafting and 3D modeling	Ashlar-Vellum
COB	Calgari trueSpace2 File Format
COB	COBOL source code file
COD	Code definition table	UUPC
COD	Datafile	Forecast Plus - Microsoft Multiplan - StatPac Gold
COD	file uncluding CODES for any program/game	many
COD	Printer code definition file	Boxer/2
COD	Program compiled code	FORTRAN
COD	Template source file	dBASE Application Generator
COD	Videotext file
COE	Coefficient file	Xilinx ISE
COF	Animation Control File	Diablo II
COL	Color palette	Autodesk Animator - many
COL	Spreadsheet	Microsoft Multiplan
COM	Command (memory image of executable program)	DOS
COM	Indirect command file (sequence of commands to be executed)	RT-11
CON	Configuration file	Simdir
CON	MSTS Consist file	MSTS
CPC	Compressed image	Cartesian Perceptual Compression
CPD	Script	Complaints Desk
CPF	Fax	The Complete Fax
CPI	ColorLab Processed Image bitmapped graphics file
CPI	MS-DOS codepage file	MODE.EXE
CPL	Control panel file	Windows 3.x
CPL	Presentation	Compel
CPMZ	ConPro/Miradi Zipfile	Miradi and ConPro
CPP	C++ language source	Watcom C/C++
CPP	Presentation	CA-Cricket Presents
CPR	Knowledge Access	GCGW
CPS	backup of startup files by QEMM (?) autoexec.cps
CPT	Encrypted memo file	dBASE
CPT	Mac file archive	COMPACT PRO
CPT	Template	CA-Cricket Presents
CPZ	Music text file	COMPOZ
CR2	Raw image format	Canon digital cameras
CRA	Advanced crack file (usually text)
CRD	Cardfile	Windows 3.x - YourWay
CRD	Map	Holux - Alan
CRD	Molecular coordinates	CHARMM, RasMol
CRDOWNLOAD	Google Chrome download in progress	Google Chrome
CRF	Cross-reference	Microsoft MASM - Zortech C++, RT-11 CREF
CRK	Crack file (usually text)
CRP	Encrypted database	dBASE IV
CRS	File Conversion Resource	WordPerfect 5.1
CRT	Terminal settings information	Oracle
CRU	Compressed file archive created by CRUSH
CS	C# source file	C#
CSD	Compact Shared Document	Dream To Reality
CSG	Batch file (Submit)	ISIS/w
CSG	Graph	Statistica/w
CSM	Borland C++ 4.x precompiled header file	BCW.EXE
CSP	PC Emcee Screen Image file	Computer Support Corporation
CSS	Datafile	CSS - Stats+
CSS	Datasheet	Statistica/w
CSS	cascading style sheet
CSV	Adjusted EGA/VGA palette	CompuShow
CSV	Comma Separated Values text file format (ASCII)
CTC	Control file	PC Installer
CTF	Character code translation file	Symphony
CTK	CommonTime Key file	CommonTime software applications
CTL	Control file	dBASE IV - Aldus Setup
CTL	BATCH control file (generated by BATCH from .BAT file)	RT-11
CTT	BATCH Temporary file	RT-11
CTX	Ciphertext file	Pretty Good Privacy RSA System
CTX	Course TeXt file	some Microsoft online guides
CTX	document	Creativyst Table eXchange
CUF	C Utilities Form definition	TCU Turbo C Utilities
CUR	Windows resource (cursor image file)	Resource Workshop - WRT - Watcom Resource Editor
CUT	Graphics format (bitmapped graphics)	dr. Halo
CV4	Color file	CodeView
CVP	Cover page	WinFax
CVS	Graphics	Canvas
CVT	Backup file for CONVERTed database file	dBASE IV
CVW	Color file	CodeView
CWEB	C Web
CWK	Datafile	ClarisWorks, Appleworks
CXX	C++ source code file	Zortech C++

D

Ext.	Description	Used by
D	D Programming Language source file	DMD
D3V	Video file	Nintendo DS (with ARME, MMCF etc.)
D4D	Data	Draw 4D object
D4P	Data	Draw 4D Pro object
D64	Commodore 64 disk image
D88	Toshiba Pasopeia D88 disk image format	A series of emulators of Japanese computers
DAA	Direct Access Archive
DAE	COLLADA file
DAF	Data file	Digital Anchor
DAT	Maxum chromatograph chromatogram	Siemens Maxum Chromatograph
DAT	LDraw (Sub)Part File, 3D Model	LDraw
DAT	Document	Microsoft Word Format (old)
DAT	data	RSNetWorx Project
DAT	Data file in special format or ASCII
DAT	Database file	Clarion (programming language)
DAT	Optical disc image (can be ISO9660, but not restricted to)	cdrdao, burnatonce
DAT	Video CD MPEG stream
DATS	Dynamic source	ATS
DB$	Temperature debug info	Clarion Modula-2
DB$	Temporary file	dBASE
DB	Database file	Paradox - XTreeGold - dbvista
DB	Configuration	dBASE IV - dBFast
DB	Multi Edit config	ME
DB2	Database	dBASE II
DB3	Database	dBASE III
DBA	Database file	Turbo Prolog - DataEase
DBA	DarkBasic source code
DBC	DataBaseContainer	Visual FoxPro
DBD	Business data	Business Insight
DBD	Debug info	Clarion Modula-2
DBF	Database file	dBASE III/IV - Visual FoxPro - dBFast - DataBoss - DBVista - CA-Clipper - Visual Objects - Alaska Xbase++ - Advantage Database Server
DBG	Debugger script	DOS debug - Watcom debugger
DBG	Symbolic debugging information	Microsoft C/C++
DBK	Database backup	dBASE IV
DBL	DIBOL source file
DBM	Datafile	DataEase
DBM	Menu template	DataBoss
DBO	Compiled program	dBASE IV
DBPro	DarkBasicPro Project
DBS	Data file used by Managing Your Money
DBS	Database in SQL Windows format
DBS	Datafile	PRODAS
DBS	Printer description file	Microsoft Word, Microsoft Works
DBT	FoxBASE+ style memo	FoxPro 2.x
DBT	Memo file for database w/same name	dBASE IV - dBFast
DBW	Windows file	DataBoss
DBX	DataBeam	GCGW
DBX	AutoCAD Database	AutoCAD
DBX	Archive File	Outlook Express
DC	CAD drawing file	DesignCAD 3000 for Windows
DC6	Image file	Diablo II
DCA	Document Content Architecture text file	IBM DisplayWrite
DCC	Animation	Diablo II
DCD	CAD Drawing File	DesignCAD 3DMax for Windows
DCF	floppy disk image	Disk Copy Fast
DCH	Schematic Drawing file	DipTrace Schematic Capture
DCI	Dreamcast Save File	Dreamcast
DCL	Delphi Control Library	Borland Delphi
DCM	DCM music module	AWAVE
DCP	OS/2 device code page	OS/2
DCS	Bitmap graphics (CYMK format)	QuarkXPress
DCS	Datafile	ACT! Activity Files
DCT	Dictionary: used by many programs with program dependent format	Clarion
DCT	Spell checking dictionary	Harvard Graphics 3.0 - Symphony
DCT	DataBaseContainer Extension	Visual FoxPro
DCU	Delphi unit (compiled)	Borland Delphi
DCW	Walter Machine Programing	Walter Profile Editor
DCX	Multi-page PCX graphics (common fax format)	Intel - SpectraFAX
DCX	DataBaseContainer Index	Visual FoxPro
DD	Macintosh file archive	DISKDOUBLER
DDA	Data	GLBasic ASCII 3D object
DDB	Bitmap graphics
DDB	Digidesign Database File	Digidesign ProTools
DDI	Disk image	DiskDupe
DDP	Device Driver Profile file	OS/2
DDS	DirectDraw Surface file	Microsoft Flight Simulator, other Microsoft programs
DEB	DEBUG script	DOS Debug
DEF	Assembly header file	Geoworks
DEF	Defaults - definitions
DEF	Linker definition file	TLink - WLink...
DEM	Demonstration
DEM	Digital Elevation Model
DEM	Graphics file	VistaPro
DEM	Vista DEM file	Meta.exe VP3
DES	Ascii text parameter description	AWAVE
DESKLINK	Windows Explorer Desktop Control (commonly "Desktop (create shortcut).DESKLINK", 0 bytes). Uses a 'special' hidden file extension (NeverShowExt flag inside the Registry), overriding the Windows Explorer option of showing/hiding file extensions.
desktop	Desktop Entry	freedesktop.org
DEV	Device driver
DEV	SYSGEN handler build procedure	RT-11
DEV	Dev-C++ project file	Dev-C++
DFD	Data Flow Diagram graphic file	Prosa
DFF	RenderWare model data (e.g. Grand Theft Auto III and later)
DFI	Outline font description	Digifont
DFL	Default program settings	Signature
DFM	Data Flow Diagram model file	Prosa
DFM	Delphi form module	Borland Delphi
DFS	Delight Sound File
DFV	Printing form (Word)	Microsoft Word
DFX	Micrografx Effects DLL
DGN	Graphics file	MicroStation
DGS	Diagnostics
DH	Dependency information for .ph	Geoworks
DHP	Dr. Halo PIC Format graphics file	Dr. Halo II - III
DHT	Datafile	Gauss
DI	D Programming Language interface file	DMD
DIA	Diagraph graphics file	Computer Support Corporation
DIB	Device Independent Bitmap	rarely used Windows 3.0 bitmap; Win - OS/2
DIC	Dictionary (e.g. from WinWord)
DIF	Borland patch data file	Borland patch
DIF	Data Interchange Format	Visicalc
DIF	OS/2 V2.2 Display Information File	OS/2
DIF	Output from Diff command - script for Patch command
DIF	SRCCOM, BINCOM output file	RT-11
DIG	Digilink	AWAVE
DIG	Sound Designer 1 audio file	AWAVE
DIP	Graphics
DIP	Watcom debug info processor	WatcomDebugger
DIP	PCB Drawing file	DipTrace PCB Layout
DIR	Dialing directory file	Procomm Plus
DIR	Directory file	VAX - CPS Backup
DIR	Movie	MacroMind Director 4.x
DIR	Directory listing file	RT-11
DIS	Distribution file	VAX Mail
DIS	Thesaurus	CorelDraw
DIZ	Description file (Description In Zip)
DJVU	DJVU Document Format, a format similar to PDF but with higher compression rates at the same quality.	DJVU
DKB	Raytraced graphics	DKBTrace
DL	Animation format (Italian origin)	Display - DL Viewer
DLD		Lotus 1-2-3
DLF	Dialogue Live Format	Produced by Exstream Dialogue and edited by Dialogue Live Editor
DLG	Dialog resource script file	Microsoft Windows SDK
DLG	Dialog resources	DN
DLG	Windows SDK dialog editor data file
DLG	Windows SDK dialog editor data file
DLL	Dynamic-link library	Windows 3.x - OS/2
DLL	Export/import filter	CorelDRAW
DLM	Microsoft File Transfer Manager	Microsoft File Transfer Manager
DLP	Data	DAQLab
DLS	Setup	Norton Disklock
DMF	Music format (Delusion Digital Music File)	Delusion
DMF	DeleD files
DMG	Apple Disk Image	Mac OS X (Disk Utility),
DMO	Demo	Derive
DMP	Dump file (e.g. screen or memory)
DMP	DUMP utility output file	RT-11
DMS	Amiga file archive	DISKMASHER
DNG	Digital Negative (DNG), a publicly available archival format for the raw files generated by digital cameras.	At least 30 camera models from at least 10 manufacturers, and at least 200 software products.
DNT	data	RSNetWorx Project
DO	Java servlet file	Web browser (Various)
DOC	A Document, or an ASCII text file with text formatting codes in with the text. This generic extension is used by many word processors.	Microsoft Word and others
DOCM	Microsoft Word 2007 Master document	Microsoft Word 2007
DOCX	Office Open XML Text document	Microsoft Word
DOF	Delphi project options file	Borland Delphi
DOG	Screen file	Laughing Dog Screen Maker
DOH	Dependency information for .poh	Geoworks
DOR	Roland Digital audio file	Roland
DOS	External command file	1st Reader
DOS	Network driver (e.g. pkt_dis.dos)
DOS	OS/2 V3 SVGA PMI-File	Svga.exe
DOS	System file for 'pure' MS-DOS usage (e.g. MSDOS.DOS, AUTOEXEC.DOS; alternate versions of MSDOS.SYS and AUTOEXEC.BAT respectively)	Windows 95, 98
DOS	Text file containing DOS specific info
DOT	Line-type definition file	CorelDRAW
DOT	Microsoft Word document template	Microsoft Word
DOTX	Office Open XML Text document template	Microsoft Word
DOX	Text file	MultiMate 4.0
DOZ	Description Out of Zip	VENDINFO
DP	Calendar file	Daily Planner
DP	Data file	DataPhile
DPR	Default project- and state-related information	Borland C++ - Delphi - C
DPX	Digital Moving Picture Exchange
DRP	Web3D File	Web3D
DRS	Display Resource	WordPerfect for Win
DRV	Driver
DRW	Designer vector graphics file	Designer - MicroGraphix
DS	TWAIN Data Source	Any twain-source must supply one xxx.ds file
DS1	Map file	Diablo II
DS4	Vector graphics	Micrografx Designer 4.x
DSC	Celestia Deep Space Catalog file	Celestia
DSC	Description file
DSC	Discard file	Oracle
DSD	Database	DataShaper
DSF	Data Storage Format	Golden Helix
DSF	Delusion Digital Sound File	Delusion
DSK	Desktop configuration	BP - DN - BC++ - TP
DSK	Disk Drivers	Novell NetWare
DSK	Logical disk file	RT-11
DSM	Digital Sound Module	DSI
DSN	Design	Object System Designer
DSP	Display parameters	Signature
DSP	Dynamic Studio Professional Module	Dynamic Studio
DSP	Graphics display driver	Dr. Halo
DSP	Norton viewer DLL	Win
DSR	Driver Resource	WordPerfect for Win
DSS	Screensaver file	DCC
DSS	Digital Speech Standard (Sound)	Digital Soup
DSS	SQL Script for .Time Framework	Exaktime
DST	WAIN (Scanner spec) data source DLL	Win
DSW	Borland C++ 4.x desktop layout file	BCW.EXE
DSY	DAISY container file	ADAKTA.EXE
DT1	Tile file	Diablo II
DT2	msn-emoticon	paint
DT_	Data fork of a Macintosh file	Mac-ette
DTA	Data file	Turbo Pascal - PC-File - Stata
DTB	Database Backup for .Time Framework	Exaktime
DTF	Database file	PFS - Q&A
DTL	Django template language	djangoproject
DTM	DigiTrekker music module	AWAVE
DTO	data	Directory Toolkit output
DTP	Desk Top Publishing Document	Timeworks / greenstreet Publisher3/ Greenstreet Publisher 4.5
DTP	Page Magic 2.0 publication	Page Magic 2.0 upgrades to Greenstreet Publisher
DTP	Publication	Publish-It! upgrades to Greenstreet Publisher
DTS	Torque Game Engine model format
DVC	Data	Lotus 1-2-3
DVDPROJ	iDVD project file	iDVD (Apple iLife '08)
DVI	DeVice Independent document	TeX
DVP	DESQView run-file	DESQView
DVP	Device parameter file	AutoCAD
DW2	Drawing	DesignCAD for DOS, & DesignCAD for Windows
DWB	Coryphaeus Software Designers Workbench	CSD
DWC	Archive	DWC
DWD	DiamondWare Digitized file	AWAVE
DWG	Drawing	AutoCAD, IntelliCAD, PowerCAD, Drafix, etc.
DX	Text file	DEC WPS/DX format - DEC WPS Plus
DXF	Dialogue Exchange Format	Exstream Dialogue
DXF	Drawing Interchange File Format vector graphics	AutoCAD, IntelliCAD, PowerCAD, etc.
DXN	Fax	Fujitsu dexNET
DXP	SpotFire data	TIBCO Spotfire
DXP	ISO creation project file	CD Burner XP Pro
DYLIB	Dynamic Library	Mac OS-X
DYN	Data	Lotus 1-2-3

E

Ext.	Description	Used by
E	E language source code	E
E2D	2-dimensional vector graphics file	Editor included in JFire
EAS	Extended file attributes	OS/2
EAR	Enterprise archive	archive
EBA	Source code	Emergence BASIC
EBJ	Error-checking object file	Geoworks
EBQ	CITE standard electronic BQ exchange file
EC	Error checking preprosessed Goc source code	Geoworks
EC	Source code	Ecere SDK
ECC	Error-checking file	dvdisaster
ECE	Escenic Contentng Engine dynamic page	Escenic
ECMS	Status document	ECMerge
ECMT	Template document / Session	ECMerge
ED5	EDMICS	GCGW
EDA	Ensoniq ASR disk image	AWAVE
EDE	Ensoniq EPS disk image	AWAVE
EDF	European data format	Medical timeseries storage files
EDF	Exchequer Document Format	IRIS Software
EDF	Macrocom Online Kitchen-planer
EDK	Ensoniq KT disk image	AWAVE
EDL	EDL	Premiere
EDQ	Ensoniq sq1,2/ks32 disk image	AWAVE
EDS	Ensoniq SQ80 disk image	AWAVE
EDT	Default settings	VAX Edt editor
EDT	Ensoniq TS disk image	AWAVE
EDT	External editors definitions	DN
EDV	Ensoniq VFX-SD disk image	AWAVE
EEB	Button bar for Equation Editor	WordPerfect for Win
EFA	Ensoniq ASR file	AWAVE
EFA	Encrypted File Archive
EFE	Ensoniq EPS file	AWAVE
EFE	Ensoniq EPS instrument file	AWAVE
EFK	Ensoniq KT file	AWAVE
EFQ	Ensoniq SQ1/SQ2/KS32 file	AWAVE
EFS	Ensoniq SQ80 file	AWAVE
EFT	Ensoniq TS file	AWAVE
EFT	High resolution screen font	ChiWriter
EFV	Ensoniq VFX-SD file	AWAVE
EFX	Fax	Everex EFax
EGA	EGA display font	Ventura Publisher
EKA	Internal data files	Borland's Eureka
EL	ELISP source code file	Emacs lisp
ELB	Synergy/DE library
ELC	Compiled ELISP code	Emacs lisp
ELFO
ELI	Archive	ELI
ELT	Event list text file	Prosa
EMAKER	E language source code (maker)	E
EMD	ABT Extended MoDule	AWAVE
EMF	Microsoft Enhanced Metafile
EML	Stationery Template	Outlook Express
EMU	Terminal emulation data	BITCOM
ENC	Encoded file - UUENCODEd file	Lotus 1-2-3 - uuexe515.exe
ENC	Music	Encore
END	Arrow-head definition file	CorelDRAW
ENFF	Extended Neutral File Format
ENG	Dictionary engine	Sprint
ENG	English documentation
ENG	Graphics file (charting)	EnerGraphics
ENV	Envelope or Environments
ENV	Enveloper macro	WOPR
ENV	Environment file	WordPerfect for Win
EPD	Publication	Express Publisher
EPI	Document	Express Publisher
EPI	Encapsulated PostScript graphic file
EPS	Encapsulated PostScript (Graphics format)	CorelDraw - PhotoStyler - PMView - Adobe Illustrator - Ventua Publisher
EPUB	Electronic Publication - (e-Reader format)	Okular (Linux) - Apple iBooks - Sony Reader - Adobe Digital Editions - Calibre (LMW)
EQN	Equation filE	WordPerfect for Win
ERD	Entity Relationship Diagram graphic file	Prosa
ERL	Erlang source code file
ERM	Entity Relationship Diagram model file	Prosa
ERR	Compiler/linker error report
ESH	Extended Shell batch file
ETH	Document	Ethnograph 3
ETF	Encrypted Text File. Used in some security programs.
ETW	Proprietary format from EnterTech for the MagicSing/Mic Karaoke product line.	Enter-Tech
ETX	Structure-enhanced text for some ascii text browsers
EUI	Ensoniq EPS family CD image	AWAVE
EVT	Events descriptions
EVY	Document	WordPerfect Envoy
EWD	Document	Express Publisher for Windows
EX3	Device driveR	Harvard Graphics 3.0
EXC	Exclude file for Optimize (do not process) (QEMM)	QEMM
EXC	REXX source code file	VM/CMS
EXE	Directly executable program	DOS
EXF	Excute file	OnHand PC
EXM	MSDOS executable, system-manager compliant (HP calculator)	HP calculator
EXP	Drawing File format	Drawing Express
EXP	Protected mode EXE by PharLap Software	PharLap
EXP	Exports Library File	VisualStudio
EXT	Extensions descriptions file
EXX	Intermediate file by MsgPut	IBM LinkWay
EZF	Fax	Calculus EZ-Fax

F

Ext.	Description	Used by
F	Archive	FREEZE
F	Fortran language source code file (in fixed form)	Many Fortran compilers
F01	Fax	perfectfax
F03	Fortran language source code file (in free form)	Many Fortran compilers
F2R	Farandole Linear Module	Farandole
F3R	Farandole Blocked Linear Module	Farandole
F4	Fortran IV source code file
F4A	Flash Video F4V with only audio (see also SWF)	Adobe Flash
F4B	Flash Video F4V audio book (see also SWF)	Adobe Flash
F4P	Flash Video F4V with digital rights management (see also SWF)	Adobe Flash
F4V	A container format for Flash Video that differs from the older FLV file format (see also SWF)	Adobe Flash
F77	Fortran language source code file (in fixed form)	Many Fortran compilers
F90	Fortran language source code file (in free form)	Many Fortran compilers
F95	Fortran language source code file (in free form)	Many Fortran compilers
F96	Fax	Frecom FAX96
FAC	see FACE
FACE	Usenix FACE graphics file
FAL	Falcon script source	Falcon
FAM	Famtasia Famicom image format	Famtasia
FAQ	Frequently Asked Questions text file
FAR	Music format (Farandole Composer Module)	Farandole
FAS	Macsyma compiled program
FAX	Fax (raster graphics in CCITT format)	most Fax programs
FBM	Fuzzy Bitmap
FC	Spell checking dictionary	Harvard Graphics 2.0
FCM	Binary file patch file (forward compression)	jlpak10.zip
FD	Declaration file	Microsoft Fortran
FD	Field offsets for compiler	DataFlex
FD	Front Door' resource files	FD
FDB	Font Definition Block	Ming library
FDS	fwNES Famicom Disk System image	fwNES
FDS	Headerless Famicom Disk System image
FDW	Form	F3 Design and Mapping
FDX	Screenplay	Final Draft
FE	Data	Surface Evolver 3D surface
FEB	Button bar for Figure Editor	WordPerfect for Win
FEI	Fatal Error Infotable	Geoworks
FES	File produced when a fileless occurrence in 3D Topicscape is exported to Windows	3D Topicscape
FF	Intelligont FIAS format
FF	Outline font description	Agfa Compugraphics
FFE	Front Fareast Famicom image format
FFF	Fax	defFax
FFI	Atech FastFont (AllType)
FFIVW	File Format for the Interchange of Virtual Worlds
FFT	Dca/FFT Final Form Text text file (DisplayWrite)
FFT	DCA/FFT Final Form Text text file	DisplayWrite
FH3	Vector graphics	Aldus FreeHand 3.x
FH4	Vector graphics	Aldus FreeHand 3.x
FI	Interface file	Microsoft Fortran
FIF	Fractal Image Format file
FIG	Figure File	MATLAB
FIL	Table Data	Audit Command Language (ACL)
FIL	File template	Application Generator
FIL	Filelist
FIL	Files list object file	dBASE Application Generator
FIL	Mirror. FIL is the name given to the saved FAT by the mirror program included in some versions of DOS and in PCTools	MS-DOS -
FIL	Overlay	WordPerfect
FIL	File which was moved to the Virus Vault by AVG
FILM	Filmkey film file	Filmkey Player
FIN	Print-formatted text file	Perfect Writer - Scribble - MINCE
FIO	Aldus PhotoStyler graphics filter
FIO	Image PALS viewer DLL
FIT	File Index Table	WindowsNT
FIT	see FITS
FIT	Fityk Script	Fityk
FITS	Flexible Image Transport System	astronomy software
FIX	Patch file
FKY	Macro file	FoxPro
FLA	Source material for Flash applications (see SWF)	Adobe Flash
FLAC	Audio codec, Audio file format
FLAME	Fractal configuration file	Apophysis
FLB	Format library	Papyrus
FLC	Animation format FLIC >320x200	AAPlay - Autodesk AniPro
FLD	Folder	Charisma
FLI	Animation format FLIC 320x200	Autodesk Animator
FLI	TeX font library	EmTeX
FLM	Film Roll	AutoCAD/AutoShade
FLP	Flstudio project file	Fruity Loops (FlStudio)
FLT	Data/file conversion filter (or overlay)	Alsud, Microsoft Word
FLT	Filter file	Micrografx Picture Publisher
FLT	MultiGen Flight
FLT	Support file - graphics filter	Asymetrix ToolBook
FLX	Animation format
FLX	Compiled binary	DataFlex
FLV	A container format for Flash Video (see also SWF)	Adobe Flash
FM	Database	FileMaker Pro
FM1	Spreadsheet format overlay	Lotus 1-2-3 release 2.x
FM3	Device driver	Harvard Graphics 3.0
FM3	Spreadsheet	Lotus 1-2-3 release 3.x
FMB	File Manager Button bar	WordPerfect for Win
FMF	Font or icon file	IBM LinkWay
FMK	Makefile	Fortran PowerStation
FMO	Compiled format file	dBASE IV
FMT	Format file	dBASE IV - FoxPro - Clipper 5 - dBFast
FMT	Gate3 format file
FMT	Style sheet	Sprint
FMV	Full Motion Video file
FN3	Font file	Harvard Graphics 3.0
FND	Files searching properties	Win95
FNI	FileNet Native Document	FileNet
FNK	FunkTracker music module	AWAVE, FunkTracker
FNM	Fannie Mae Residential Loan Data (RLD) format for mortgage submission to DO/DU.	Desktop Originator
Fnn	DOS screen text font - height nn pixels	fntcol13.zip
FNT	Font file	many
FNX	Inactive font	Exact
FO1	Font file	Borland Turbo C
FO2	Font file	Borland Turbo C
FOG	Fontographer Database File	Fontographer3.5
FOL	Folder of saved messages	1st Reader
FON	Log of all calls	Procomm Plus
FON	Terminate phonebook	Terminate - Terminator - Telix
FON	Windows bitmapped font file	Win
FONT	Font data	unix
FOP	Freedom of the Press graphic file
FOR	Form	WindowBase
FOR	Fortran language source file	many
FOT	Installed Truetype font	Windows Font Installer
FOX	Foxbase executable (precompiled .prg)	FoxBase
FP	Final Page file	FoxPro for DOS
FP	Tiff file	TIFF/IT P1
FP	Video file	DVICO/TVIX MPEG1 video file
FP3	Database	FileMaker Pro
FP4	Database	FileMaker Pro
FP5	Database	FileMaker Pro
FP7	Database	FileMaker Pro
FPC	Catalog	FoxPro
FPD	TMT Pascal compiled unit	TMT Pascal
FPM	Configuration file	FoxPro for MacIntosh
FPT	Foxpro memo field tables	FoxPro
FPU	Configuration file	FoxPro for Unix
FPW	Floorplan drawing	FloorPLAN plus for Windows
FPW	Configuration file	Visual FoxPro
FPX	FlashPix Bitmap Image File	FlashPix
FR?	Packed mail	FTN software
FR3	Renamed dBASE III+ form file	dBASE IV
FRF	FontMonger Database file	FontMonger
FRG	Uncompiled report file	dBASE IV
FRL	GP-Forth library	GP-Forth
FRM	Registration or other form
FRM	Report file	dBASE IV - Clipper 5 - dBFast
FRM	Visual Basic Form	Visual Basic
FRO	Compiled report file	dBASE IV
FRP	Form	PerForm PRO Plus - FormFlow
FRS	Screen Font Resource	WordPerfect for Win
FRT	Additional (FPT) report description file	FoxPro
FRT	GP-Forth source file	GP-Forth
FRX	Main (DBF) report description file	Visual FoxPro
FRX	Visual Basic binary program file	Visual Basic
FSA	Applied Biosystems Genetic Analysis data file	GeneScan
FSIM	Simulation File Format	Loudsoft
FSL	Form	Paradox for Windows
FSM	Farandole Composer WaveSample	Farandole
FSPROJ	Habanero Firestarter project	Habanero Firestarter
FST	Linkable program	dBFast
FST	Temporal database file	GTKWave data file
FSTICK	Temporal database file	Flash Joystick
FSX	Data	Lotus 1-2-3
FTD	Falcon dynamic template	Falcon
FTM	Fielded Text Meta - Contains schema/Meta for a Fielded Text file	Fielded Text
FTM	Font file	Micrografx
FTX	Declared Fielded Text	Fielded Text
FTXT	text	Cloanto text document
FTP	Configuration	FTP Software PC/TCP
FUK	Map File	Postal 2
FW	Database	FrameWork
FW2	Database	Framework II
FW3	Database	Framework III
FWEB	Fortran WEB
FX	On-line guide	FastLynx
FXD	Phonebook	FAXit
FXP	Foxpro executable (precompiled .prg)	Visual FoxPro
FXS	FAX Transmit Format graphics file	WinFax
FYF	FileLoc	FyTek, Inc.

G

Ext.	Description	Used by
G	Data chart	APPLAUSE
G16	GoldED for DOS compiled config	GOLDED.EXE
G3D	Glest model file	G3D viewer
G3P	data	Grand Prix 3 car physics
G8	Raw graphics file (one byte per pixel) plane three	PicLab - Cubicomb Picturemaker
GAF	Globa Game Engine audio format	Globa Game Engine
GAM	Fax	GammaFax
GAMEPROJ	Gamesalad game project format	GameSalad
GB	Game Boy ROM
GB1	Game Maker backup file (can also be GB2, GB3, etc.)
GBA	Game Boy Advance ROM
GBC	Game Boy Color ROM
GBL	Genesis Bitmap Layout
GBL	Global definitions	VAXTPU editor
GBL	Global module in Basic programs
GBP	Genesis Bitmap Pattern
GBR	GIMP brush
GC1	Lisp source code	Golden Common Lisp 1.1
GC3	Lisp source code	Golden Common Lisp 1.3
GCA	IBM GOCA	GCGW
GCD	Graphics
GCD	General content descriptor	Wireless devices
GCD	Generic Cadd drawing	Generic Cadd, Visual Cadd
GCF	Game cache file	Steam content delivery system
GCH	GNU preprocessed C++ header file	GNU C++ compiler
GCI	Nintendo GameCube save file	Nintendo GameCube
GCX	Graph file	Mac OS X Grapher
GD3	Game Doctor Super NES ROM image
GDF	General Data Format for Biomedical Signals	Biomedical signal processing, Brain Computer Interfaces
GDF	Dictionary file	GEOS
GDF	Geographical Data Format	Various mapping software
GDF	IBM Graphics Data Format	Legacy IBM systems
GDL	Data	ArchiCAD model
GDS	McDonnell-Douglas Things
GE	GEcho config file	GEcho
GED	GEDCOM	Genealogy data exchange
GED	EDITOR's native file format	Arts & Letters
GED	GoldED for DOS compiled config file	GOLDED.EXE
GED	Graphics editor file	EnerGraphics
GED	Game Editor Data / project file	Game Editor
GEM	Vector graphics file	GEM - Ventura Publisher
GEN	Compiled template	dBASE Application Generator
GEN	Generated text	Ventura Publisher
GEO	Geode	Geoworks
GEO	GEOS specific file (application)	GEOS
GEO	GoldED for OS/2 compiled config file	GED2.EXE
GEX	GEcho config file	GEcho
GFB	Compressed GIF image created by GIFBLAST	gifblast.exe
GFO	SGI Radiosity
GFT	Font	NeoPaint
GFT	GEM-translator font file
GFX	Instant Artist graphics Files	Instant Artist
GFX	PCBoard @X-coded colorful text	GFX2COM - GFX2EXE
GHO	Norton Ghost File (first file)	Symantec
GHS	Norton Ghost File (split file)	Symantec
GHW	GHDL Wave file	GHDL/GTKWave data file
GIB	Chart	Graph-in-the-Box
GIB	GIMP animated brush
GID	Help index	windows 95 help
GIF	Compuserves' Graphics Interchange Format (bitmapped graphics)	QPeg - Display - CompuShow
GIW	Presentation	Graph-in-the-Box for Windows
GKH	Ensoniq Disk Image (VFX, SD, EPS, ASR, TS)	Ensoniq
GKS	Graphics Kernel System
GL	Animation format	grasprt.exe, PV
GL	Animation	GRASP GRAphical System for Presentation
GLB	Global module in Basic programs
GLM	Datafile	Glim
GLO	Global module in Basic programs
GLS	Datafile	Across
GLY	Winword Glossary	Microsoft Word
GM6	Game Maker Editable file as of version 6.x
GMD	Game Maker Editable file up to version 5.x
GMF	CGM graphics file	APPLAUSE
GMK	Game Maker Editable file as of version 7.x or 8.x
GML	Game Maker GML file
GMOD	Data	Golgotha 3D model
GMP	Geomorph tile map	SPX
GMS	Ghost Mouse Script
GMS	Gesture and Motion File Formats
GMT	data	RFactor car physics
GOC	Goc source code file	Geoworks
GOE	GOES graphic file
GOH	Goc header file	Geoworks
GP5	Guitar Pro 5 song	Guitar Pro 5
GP	Geode parameter file	Geoworks Glue
GP4	data	Grand Prix 4 car physics
GPH	Graph	Lotus 1-2-3/G
GPK	Omnigo program package
GPX	GPS eXchange Format
GR2	Screen driver	Windows 3.x
GRA	Datafile	SigmaPlot
GrADS	Metafile
GRAFFLE	OmniGraffle graph file
GRASP	Graphical System for Presentation
GRB	T-FLEX CAD file	Top Systems
GRB	MS-DOS Shell Monitor file	MS-DOS 5
GRD	Drivers for GRX (graphics library)	GRX (c) Free Soft. Found.
GRDNT	Image format used in the core of some very obscure customized operating systems to represent gradients; see also SCTOR
GRE	data	Grenoble Thermal ellipsoids Plot Program
GRF	Graph file	Graph Plus - Charisma
GRIB	Gridded Binary
GRN	Drivers for GRX (graphics library)	GRX (c) Free Soft. Found.
GRP	Group file	Windows 3.x - Papyrus
GRP	Pictures group	PixBase
GRY	Graphics format (RAW GREYz)
GS1	Presentation	GraphShow
GS3	data	GameStarter
GSA	data	Microsoft Office Groove Space Archive
GSD	Vector graphics	Professional Draw
GSM	Raw GSM 6.10 audio stream	AWAVE
GSP	Geometer's Sketchpad
GSW	Worksheet	GraphShow
GTA	data	Microsoft Office Groove Tool Archive
GUP		PopMail
GV	GrandView outline file
GVO	Data	GFXFX Vector Object
GWI	Groupwise File	Local saved Email
GXL	Graphics library	Genus
GZ	Archive	GNU zip - WinZipNT
GZR	data	GunZ action replay

H

Ext.	Description	Used by
H!	On-line help file	Flambeaux Help! Display Engine
H!	Pertext database	HELP.EXE
H--	C—language header	Sphinx C--
H	Header file (usually C language)	Watcom C/C++
H++	Header file	C++
HA	Archive	HA
HAL	Data file	Hyper Access Lite OS/2
HAM	Disk Drivers NPA	Novell NetWare
HAM	Hold And Modify	Deluxe Paint image file
HAP	Archive	HAP3
HBC	Compressed Archive File (Shrink Algorithm)	Hyperbac
HBC	Compressed Archive File (Shrink Fast Algorithm)	Hyperbac
HBE	Compressed, Encrypted Archive File (Shrink & AES256-bit Encryption)	Hyperbac
HBK	MathCAD handbook	MathCAD
HC	Header file
HCG	Document	HCLab
HCGS	Document	HCLab
HDD	data	disk image
HDD	HotDisc Designer label
HDF	Amiga Hard Disk Image
HDF	Help file	Help Development Kit
HDF	Hierarchical Data File graphics file	SDSC Image Tools
HDL	Alternate download file listing	Procomm Plus
HDMP	heap dumpfile
HDR	Datafile	Egret
HDR	Message header text	Procomm Plus - 1st Reader
HDR	PC-File+ Database header
HDR	SPOT image file
HDS	Hierarchical Data System
HDW	Vector graphics	Harvard Draw
HDX	Help index	AutoCAD - Zortech C++
HDZ	Amiga Zip compressed Hard Disk Image
HEP	Novell Help Librarian Data File	Novell NetWare
HEX	Hex dump
HFI	HP Font Info file	GEM
HGL	Highlight groups definitions	DN
HGL	HP Graphics Language graphics file
HH	C++ header file
HHH	Precompiled header file	Power C
HHP	Help information for remote users	Procomm Plus
HI	Game high scores table
HIN	Molecule	HyperChem
HIS	History of executing/viewing/editing	DN
HIS	Yard Information File	FYM
HKM	Stores sound in a bitmapped graphics file
HLB	Help library	VAX
HLP	Help file	WinHelp, Help Explorer Viewer
HLX	Multi Edit help file	MultiEdit 5.0
HLZ	Multi Edit packed help file	MultiEdit
HMI	Music format (MIDI)
HMM	Alternate Mail Read option menu	Procomm Plus
HMP	Music format (MIDI)
HMP	Hump Setup File - Obsolete as of version 2.4 (See SET and SWT files)	FYM
HNC	CNC program files Heidenhain (?) dialog
HOF	Hall Of Fame (game scores)
HOM	CAD Software Data File	PLXHOME
HP	Printout file for HP printers/plotters (HP/GL)
HP8	ASCII text HP Roman8 character set	NewWave Write
HPF	HP LaserJet fonts	PageMaker
HPG	see HPGL
HPGL	Plotter file vector graphics (Hewlett-Packard Graphics Language)	AutoCad - Harvard Graphics
HPI	Font information file	GEM
HPJ	Help project	Microsoft Help Compiler for Windows - HC.EXE
HPK	Archive	HPACK
HPM	Alternate Main menu for privileged users	Procomm Plus
HPM	EMM text	HP NewWave
HPM	High Performance Map	Quaestor 1.x
HPP	C++ header file	Zortech C++ - Watcom C/C++
HPPCL	Hewlett-Packard Printer Control Language
HQX	Archive (ASCII Mac)	BINHEX
HRF	Graphics file (Hitachi Raster Format)
HRM	Alternate Main menu for limited/normal users	Procomm Plus
HRZ	Graphics format	SSTV
HS2	Monochrome image	Postering
HSC	2-op FM music	HSC tracker - hscplay.exe
HSH	Disk image hash file	DriveSnapshot
HSI	Handmade Software Inc. graphics file almost JPEG	Image Alchemy
HST	History file	Procomm Plus
HTM	see HTML
HTML	Hypertext Markup Language (WWW)	Netscape - Mosaic - many
HTX	Hypertext file
HWA	Hollywood applet	Hollywood
HWD	Presentation	Hollywood Designer
HWP	Hangul Word Processor Document	Hangul (word processor)
HWS	Hollywood script	Hollywood
HXM	Alternate Protocol Selection menu for all users	Procomm Plus
HXS	Microsoft Help 2 compiled help file	Microsoft Windows, Help Explorer Viewer
HXX	C++ header file
HY1	Hyphenation algorithms	Ventura Publisher
HY2	Hyphenation algorithms	Ventura Publisher
HYC	Data	WordPerfect
HYD	Hyphenation dictionary	WordPerfect for Win
HYP	Archive	HYPER

I

Ext.	Description	Used by
I	Preprocessor output file	Borland C Preprocessor
IAK	Internet Access Kit	OS/2
IAM	Assembly file	Autodesk Inventor
IAX	Bitmap graphics (IBM Image Access eXecutive)
IAX	data	InstallAnywhere.NET project
IBG	PDS graphic file
IBM	Archive (Internal IBM only)	ARCHDOS
ICA	Bitmap graphics (Image Object Content Architecture)
ICB	Bitmap graphics
ICC	ICC configuration
ICE	Archive	Cracked LHA (old LHA)
ICM	ICC configuration
ICN	ICON source code file
ICO	Icon file	ICONEDIT.EXE; Microsoft Windows
ID	Disk identification file
IDB	IDA database	IDA
IDB	VC++ Minimum Rebuild Dependency File	Visual C++
IDC	IDA C language source	IDA
IDE	Borland C++ 4.x IDE project	BCW.EXE
IDF	MIDI instrument description
IDS	IDA imported names format	IDA
IDW	Vector graphics	IntelliDraw
IDW	Drawing file	Autodesk Inventor
IDX	Index	many - FoxPro; also unrelated Quicken file format.
IFD	Form	JetForm Design
IFF	Interchange Format File (IFF)	EA Software - Convert (C) Villena - Amiga
IFF	Sun TAAC Image File Format	SDSC Image Tool
IFP	Script	KnowledgeMan
IFS	Fractal image compressed file	Yuvpak
IFS	Iterated fractal system file	IFS Creation Kit, Apophysis
IFS	Installable file system	OS/2
IGES	Initial Graphics Exchange Specification
IGF	Inset Systems	GCGW
IGC	Flight tracks downloaded from GPS devices in the International Gliding Commission's prescribed format
IHP	Watcom help file	whelp.exe
IHS	Inbound History	Bink/+
IIW	Power Point Image Importer Wizard
IL	hDC Designer Icon Lin dll format
ILB	Data	Scream Tracker
ILG	data	LaTeX Index Generation log
ILK	Outline of program's format	Microsoft ILink incremental linker
IM	Auran Jet indexed mesh file	Trainz
IM8	Sun raster graphics file
IMA	Mirage vector graphics	EGO - Chart - Autumn
IMG	ADEX graphic file
IMG	Disk Image	NC 5.0
IMG	GEM bitmapped graphics file	Ventura
IMG	Image for Windows/Image for DOS Disk image	TeraByte, Inc. dba TeraByte Unlimited
IMG	Vivid IMG file
IMI	image	Magellan Meridian map
IMI	image	Magellan eXplorist map
IMP	Spreadsheet	Lotus Improv
IMQ	Image presentation	ImageQ
IN	Design II for Windows INput file
IN$	Installation file	HP NewWave
IN3	Input device driver	Harvard Graphics 3.0
INB	Test script	Vermont HighTest
INC	Include file	several programming languages
IND	Data Index	dBASE IV
INDD	InDesign Document	Adobe InDesign
INF	Information text file (ASCII)
INF	Install script
INF	OS/2 hypertext help system file	VIEW.EXE
INF	Type 1 LaserJet font information file	soft font installers
INFO	GNU info reader (output from Texinfo)	info (Unix)
INFO	Icon Data (Amiga)
INGR	Intergraph Raster File Format
INI	Initialization file
INK	Pantone reference fills file	CorelDRAW
INS	Data	WordPerfect
INS	Ensoniq Instrument File	Ensoniq
INS	Installation script	1st Reader
INS	Instrument music file (Adlib)
INT	Borland Interface Units
INT	Program saved in Internal (semi-compiled) format	Signature
INT	Source of Borland interface module
INX	Index	Foxbase
IO	Archive	CPIO
IOB	3d graphics database in TDDD format
IOC	Organizational chart	Instant ORGcharting!
ION	4DOS descript.ion file (file descriptions)	4DOS
IP	Immortal Player file	Immortal Player
IPC	Intellitec Program Configuration - used to configure vehicle electronics	Intellitec
IPF	Interchangeable Preservation Format	SoftPres
IPG	iPod game file	iTunes and iPod
IPH	Hi-Res Image	InterPaint
IPL	Pantone Spot reference palette file	CorelDRAW
IPN	Intecplan project	Intecplan Business Plan Software
IPS	IPS Patching Format (International Patching System)[citation needed]	Rom hacking community
IPT	Part file	Autodesk Inventor
IPT	MultiColor Image	InterPaint
IRRMESH	static irrMesh files
IRS	Resource (WordPerfect) standard.irs	WordPerfect
IRT	Data	IRIT 3D model
IRTR	Graphicon-2000 Interactive Real-Time PHIGS
ISD	Spelling Checker dictionary	RapidFile
ISH	Archive	ISH
ISMA	Output Video file	Islam Abusa'a Software
ISO	ISO-9660 table	see: List of ISO image software
IST	Digitrakker Instrument File	AWAVE
IT	Impulse Tracker music file	Impulse Tracker
IT	Settings	intalk
ITF	Interface file	JPI TopSpeed Pascal
ITL	iTunes music library
ITN	Itinerary file	TomTom PNDs
ITT	IconTweaker Theme
IV	SGI Inventor
IV-VRML	Inventor VRML Format
IVE	OpenSceneGraph 3D model
IVI	Image file	ImmerVision
IVL	Lensflare file	ImmerVision
IVP	Panorama file	ImmerVision
IVU	User Interface file	ImmerVision
IW	Presentation flowchart	IconAuthor - HSC InterActive
IWA	Text file	IBM Writing Assistant
IWB	Information WorkBench	Prodeo
IWD	Call of Duty Map - Game Data Archive	Activision, Inc.
IWP	Text file	Wang
IX	data	dtSearch index
IZT	Izl binary token file	IZL

J

Ext.	Description	Used by
J2C	JPEG 2000 image
JAM	Jam messagebase	FTN software
JAM	Jam music score	Jam
JAR	Archive	JAR. Java Games and Applications
JAS	see JASC
JASC	Graphics format (JASC)
JAV	see JAVA
JAVA	Java source code file
JBD	Datafile	SigmaScan
JBIG	Joint Bilevel Image Group
JBX	Project file	Project Scheduler 4
JCN	JobClock.Net Synch File
JET	Fax	Hybrid JetFax
JFF	see JFIF
JFIF	JPEG File Interchange Format
JIF	see JFIF
JMS	Music format (JMusic file)	UltraForce
JOB	Gravostyle engraving pattern file	Gravostyle/Gravograph
JOB	QUEUE output file	RT-11
JOR	Journal file SQL
JOU	Journal backup	VAX Edt editor
JP2	JPEG 2000 image
JPC	Graphics	Japan PIC
JPEG	Joint Photography Experts Group graphics file format	QPeg - FullView - Display
JPG	see JPEG
JRE	Java Runtime Environment	Java
JRN	JMP journal	JMP
JSP	Java Server Pages
JS	JScript script file	Javascript
JTF	Fax	Hayes JT Fax
JTF	Graphics (TIFF file with JPEG compression)
JK	Root File of a lol	Earl Grey
JVX	Data	JavaView object
JW	Text document	JustWrite
JWL	Library	JustWrite
JZZ	Spreadsheet	Jazz

K

Ext.	Description	Used by
K2A	Data	Prince of Persia 3D object
K3D	Description of macro language 3DS	3DS
KAP	Map Info Sea Chart
KAR	Music format (Karaoke)	ITune 1000.Corp
KAR	Precompiled .prg for KARAT	Rus. FOX+ 2.0
KB	Keyboard script	Borland C++ 4.5
KB	Program source	Knowledge Pro
KBASIC	Source	KBasic
KBD	Keyboard mapping	LocoScript - Signature - Procomm Plus
KBM	Keyboard mapping	Reflection 4.0
KCL	Lisp source code	Kyoto Common Lisp
KDB	KeePass 1.x database file	KeePass
KDBX	KeePass 2.x database file	KeePass
KDC	Kodak Digital Camera (graphics)	PhotoEnhancer by PictureWorks
KEP	(unknown)	(unknown)
KEX	Kedit Macro File	Kedit
KEY	Datafile	Forecast Pro
KEY	Keynote presentation file	Keynote (Apple iWork '08)
KEY	Keyboard macros
KEY	OS/2 archive .key-file (i.e. OS2.KEY)	OS/2
KEY	Security file e.g. Shareware Registration info
KFN	complex music format|	Karafun Karaoke(R)
KFX	Kofax Group	GCGW
KIT	Power Chords drum kit file	Power Chord
KMC	KatzReview's MegaCrammer
KML	Kedit Macro Library Keyhole Markup Language	Kedit Google Earth
KMY	data	KMyMoney
KMZ	Keyhole Markup Language (Zip compressed)	Google Earth
Knn	Database key file	Clarion
KNO	Personal Knowbase data file	Personal Knowbase
KPL	source code	Phrogram
KPP	Toolpad	SmartPad
KPS	IBM KIPS bitmap graphics
KR1	Kurzweil 2000 sample file	AWAVE
KR2	Kurzweil 2000 sample file	AWAVE
KRZ	Kurzweil K2000 File	Kurzweil
KS	Source code	KonsolScript Document
KS3	Data	3D Forgastest Editor object
KTU	Know The Unknown Online Service Packs	Unknownsoft
KWB	Knowledge WorkBench	Prodeo
KYB	Keyboard mapping	FTP Software PC/TCP

L

Ext.	Description	Used by
L	LEX source code file
L	Linker directive file	WATCOM wlink
L	LISP source code file
LA0	Datafile	SCUMM index file
LAB	Datafile	NCSS - SOLO
LAB	Mailing labels	Q+E for Microsoft Excel
LAN	Erdas image file
LAN	LAN Drivers	Novell NetWare
LAY	Word chart layout	APPLAUSE
LBG	Label generator data	dBASE IV
LBL	Label	dBASE IV - Clipper 5 - dBFast
LBM	Graphics format (Amiga)	Pic-view - Deluxe Paint
LBM	Linear bitmap graphics	XLib
LBO	Compiled label	dBASE IV
LBR	.LBR Archive	for CP/M and MS-DOS using the LU program
LBR	Display driver	Lotus 1-2-3
LBT	Additional (FPT) label description file	FoxPro
LBX	Main (DBF) label description file	FoxPro
LCF	Linker Control File	Norton Guides compiler
LCH	Chart	IBM Works for OS/2
LCK	Lockfile	Paradox
LCL	Data (FTP Software PC/TCP)
LCL	Data	FTP Software PC/TCP
LCN	Lection	WordPerfect
LCS	Datafile	ACT! History Files
LCW	Spreadsheet	Lucid 3-D
LD	Long Distance codes file	Telix
LDA	Absolute binary file (load image)	PDP-11, RT-11
LD1	Overlay file	dBASE
LDB	Data filer database	IBM Works for OS/2
LDB	Overlay file	Microsoft Access
LDF	Data filer form	IBM Works for OS/2
LDF	Library definition file	Geoworks Glue
LE	DOS/4GW executable image	DOS/4GW PM 32X DOS Extender
LES	Lesson (check *.cbt)
LEV	Level file	NetHack 3.x
LEX	Dictionary	Microsoft Word - Lexicon
LFL	LucasArts resource file
LFD	LucasArts resource file	LucasArts games
LFT	Laser printer font	ChiWriter
LG	Logo procedure definitions	LSRHS Logo
LGO	Logo for header and footer	SuperFax
LGO	Startup logo code	Windows 3.x
LHA	Archive	LHA/LHARC
LHW	Amiga archive	LHWARP
LIB	Library file	several programming languages
LIC	License file used by some programs to put their license on disk
LIF	Archive
LIF	CA Clipper packed file	CA Clipper installer
LIF	Logical Interchange Format data file	Hewlett-Packard
LIM	Archive	LIMIT
LIN	Line types	AutoCAD
LIS	Listing	VAX
LIT	Microsoft E-book file	Microsoft Reader
LIT	Web3D File	Web3D
LIX	Log file (history)	Audit Command Language (ACL)
LJ	Text file for HP LJ II printer
LL3	LapLink III related file (document)	LapLink III
LM	Auran Jet LOD mesh table (text file to control LODs)	Trainz
LMP	Doom lump (data file, commonly "demo" recordings)	Doom - Doom2
LNG	Language definition file
LNK	Linker response file	.RTLink
LNK	Linker script
LNK	Windows 95 shortcut	Windows 95
LNK	Windows XP shortcut	Windows XP
LOD	Load file
LOG	Log file	Numerous systems
LOM	3D Model	Lock On: Modern Air Combat
LPC	Printer driver	TEKO
LRC	Lyrics data
LRF	Linker response file	Microsoft C/C++
LRF	Unencrypted BroadBand eBook file	Sony Librie eBook reader
LRP	Report	IBM Works for OS/2
LRS	Language Resource File	WordPerfect for Win
LRX	Encrypted BroadBand eBook file	Sony Librie eBook reader
LSA	Lightscape Technologies ASCII
LSB	Lightscape Technologies Binary
LSP	LISP source code file	Xlisp, AutoLISP
LSS	Spreadsheet	Legato - IBM Works for OS/2
LST	Aus. BOM Hourly weather Data
LST	Filelist	FRQView
LST	Keyboard macro	1st Reader
LST	List file (archive index - compiler listfile)
LST	Listing (e.g. source code)
LST	Map list	Holux - Alan
LST	Spool file	Oracle
LST	SLP output file	RT-11
LTA	Data	LithTech ASCII 3D object
LTM	Form (Lotus Forms)	Lotus
LUA	Lua script file	Microsoft Visual C++, Notepad++
LUW	label data file	Labels Unlimited for Windows
LUX	2D and 3D graphics data file	Foliomap and Spectramap
LUZ	3D graphics data file	Spectramap CUDA
LWD	Text document	LotusWorks
LWO	Lightwave Object Format
LWP	Word processor	IBM Works for OS/2, Lotus Wordpro
LXF	Lego Exchange Format	Lego Digital Designer data file
LXO	Luxology scene	modo3D software
LXT	Temporal database file	GTKWave data file
LY	LilyPond Notation File	LilyPond
LYR	Lyrics (ASCII)
LZ	Archive	Lzip
LZD	Difference file for binaries	LDiff 1.20
LZH	Archive	LHA/LHARC
LZS	Archive	LARC
LZW	Archive	LHWARP
LZX	Amiga Archive	LZX

M

Ext.	Description	Used by
M	Mathematica Package File	Mathematica
M	MATLAB M-File	MATLAB
M2	WoW Model Object file	Blizzard Entertainment games (World of Warcraft/Warcraft series)
M2TS	MPEG 2 Transport Stream	Various media playback devices / software
M3U	M3U playlist file	Winamp, XMMS
M3U8	Unicode version of M3U playlist file (UTF-8)	Winamp, XMMS
M4A	Advanced Audio Coding
M4r	iPhone ringtone	iTunes and iOS devices
M7P	Multilizer 2007 and 2009 localization project file	Multilizer
M8M	8MAM8 Model File
MAFF	Mozilla Archive Format	Mozilla Firefox (with add-on)
MAI	Mail	VAX
MAK	Makefile
MAK	Project file	VB - VC ++
MAN	User guide (manual)
MANAGER	Accounting data file	Manager - free accounting software
MAP	Color palette file
MAP	Format data	Micrografx Picture Publisher
MAP	Linker map file
MAP	Map file (usually created by compilers)
MAP	Map	Atlas MapMaker
MAP	Network map	AccView
MAP	Game map for Duke Nukem 3D
MAR	Assembly program	VAX Macro
MAR	Microsoft ARchive	MSN Explorer (possibly other Microsoft products too)
MAR	Mozilla ARchive	Mozilla Updater (used to house binary updates to products)
MAS	SmartMaster set	Freelance Graphics
MAT	Data	MATLAB
MAT	Microsoft Access Table	Microsoft Access
MAX	MAX source code file
MB	Memo field values for database	Paradox
MBK	Multiple index file backup	dBASE IV
MBX	Mailbox data	Eudora/ZERBERUS
MCC	Configuration file	Mathcad
MCD	MathCad file	MathCad
MCF	Font file	Mathcad
MCF	Photo book or photo calendar layout file	FotoInsight Designer
MCF	Multimedia Container Format (predecessor of Matroska)
MCI	MCI command script	Media Control Interface
MCL	Multi Edit macro library	Multi Edit
MCL	Cartesian manipulator for laser systems
MCP	Application script	Capsule
MCP	Printer driver	Mathcad
MCR	Minecraft saved world "region" file.	Minecraft
MCW	Text file	MacWrite II
MDL	GoldSrc Model File (Quake-Based Engine)	Valve Corporation
MDL	Source Engine Model File	Valve Corporation
MDL	Quake 1 Model File	id Software
MD2	Quake 2 Model File	id Software
MD3	Quake 3 Model File	id Software
MD5	Doom 3 and Quake 4 Model File	id Software
MD	Archive	mdcd10.arc
MDA	Data	Microsoft Access
MDA	Microsoft Access system database	Microsoft Access
MDB	Microsoft DataBase	Microsoft Access
MDF	Several uses
MDL	Model	3D Design Plus or Simulink
MDL	Spreadsheet	CA-Compete!
MDM	Modem definition file	TELIX
MDMP	Mini dumpfile
MDR	Microdrive file	ZX Spectrum emulator by g.a.lunter
MDS	Midi Session	Sound Imp.
MDT	Data table	Microsoft ILink incremental linker
MDX	Multiple index file	dBASE IV
MDZ	Text description of music module	Cubic Player - Cross-View
ME	MultiEdit configuration	MultiEdit
ME	Text file READ.ME
MEB	Macro Editor bottom overflow file	WordPerfect Library
MEC	MECCA source	Maximus
MED	Macro Editor delete save	WordPerfect Library
MED	Music format	MED/OctaMED
MEM	Macro Editor macro	WordPerfect Library
MEM	Memory variable save file	dBASE IV - FoxPro - Clipper
MEM	Memos datafile	Clarion
MEM	Mnemosyne database	Mnemosyne; other spaced repetition software
MEQ	Macro Editor print queue file	WordPerfect Library
MER	Macro Editor resident area (vakioalue)	WordPerfect Library
MES	Macro Editor work space file	WordPerfect Library
MES	Message
MET	Document	Omnipage Pro
MET	Macro Editor top overflow file	WordPerfect Library
MET	OS/2 graphics metafile	PICVIEW.EXE
MEU	Menu group	DOS Shell
MEX	Macro Editor expound file	WordPerfect Library
MEX	MEX file (executable command)	Matlab
MF	Metafont file	TeX
MFA	Source code file	Multimedia Fusion 2 / The Games Factory 2
MFF	MIDI	Cakewalk, MTPro 4
MFM	Music format	DMP
MGF	Font	Micrografx
MGF	Materials and Geometry Format
MGX	Designer 4.1 Drawing	Designer 4.1
MHT	Web Archive Single File
MIB	Snmp MIB file
MID	Standard MIDI file	music synthetizers, Winamp
MIDI	See MID
MIFF	Magick Image File Format
MII	Datafile	MicroStat-II
MIME	Message in MIME format (RFC822)
miniUSF	Nintendo proprietary MIDI file format for the Reality Signal Processor (Nintendo 64)	Nintendo 64 games
MIO	MyInfo topic	Milenix MyInfo
MIS	Mission, used by many games
MIX	Object file	Power C
MK	Makefile
MKE	Makefile	Microsoft Windows SDK
MKG	Makefile
MKI	Graphics format (Japan MKI)
MKI	Japanese graphics MAKIchan format	MagView 0.5
MKS	Data	TACT
MKV	Matroska Multimedia Container	Media Player Classic, Windows Media Player, Matroska Splitter
ML3	Project	Milestones 3.x
MLB	Macro library file	RT-11, Symphony
MLI	3DS Materials Libraries	3D Studio
MLRAW	Data	Moonlight Creator RAW format 3D object
MLV	LabVIEW MathScript
MM	Text file	MultiMate Advantage II, FreeMind mind map file (XML)
MMF	Mail message file	Microsoft Mail
MMM	Multimedia movie file, RIFF RMMP format	MacroMind Director 3.x
MMO	Memo writer file	RapidFile
MMP	Output video format from Bravado board
MN	MuPAD Pro Notebook	Workspace file of MuPAD (integrated in Matlab)
MND	Menu source	AutoCAD Menu Compiler
MNG	Map	DeLorme Map'n'Go
MNT	Additional (FPT) menu description file	FoxPro
MNT	Menu memo	FoxPro
MNU	Advanced macro file	HP NewWave
MNU	Menu	AutoCAD Menu Compiler - Norton Commander - Signature
MNU	Microsoft Mouse menu (for DOS apps)
MNX	Compiled menu file	AutoCAD
MNX	Main (DBF) menu description file	FoxPro
MNY	Account book	Microsoft Money
MO?	Packed mail	FTN software
MOB	Device definition file	PEN Windows
MOBI	eBook	Mobipocket
MOD	Modula language source
MOD	MODULA-2 source code file	Clarion Modula-2
MOD	Module—used by Windows for DLL which implement DOS support	Win
MOD	Music format (Amiga module)	DMP - ST - MDP - VP
MOL	MOD4WIN PlayList	Mod4Win
MOL	MDL Molfile	RasMol
MOL2	Tripos’ Sybyl MOL2 Format	SYBYL, RasMol
MON	SYSGEN monitor build procedure	RT-11
MON	Monitor description	ReadMail
MOP	MOPAC input file	MOPAC, RasMol
MOV	Animation format (Mac)	QuickTime
MOV	Movie file	AutoCAD AutoFlix
MP2	Mpeg audio file	Winamp, xing
MP3	MPEG audio stream, layer 3	AWAVE, CoolEdit(+PlugIn), Winamp, many others
MP4	multimedia container format, MPEG 4 Part 14	Winamp
MPA	MPEG audio stream, layer 1,2,3	AWAVE
MPC	Calendar file	Microsoft Project
MPC	Musepack audio
MPEG	multimedia containter format, video, audio	MPEG Player, Winamp
MPG	see MPEG
MPKG	Multipackage installer script	Mac OS X
MPL	MediaRack Midi Playlist	MediaRack
MPM	MathPlan macro	WordPerfect Library
MPP	Project file	Microsoft Project
MPPZ	MagicPlot project file	MagicPlot
MPQ	Mo'PaQ Archive	Blizzard games
MPR	Generated executable menu file	FoxPro
MPR	Multilizer 5.x and 6.x localization project file	Multilizer
MPR	Command & Conquer: Red Alert 2 map file	Red Alert 2
MPT	Bitmap graphics (Multipage TIFF)
MPV	View file	Microsoft Project
MPX	Compiled executable menu file	FoxPro
MPX	Video format
MPZ	Miradi Project Zipfile	Miradi
MRB	Multiple Resolution Bitmap graphics file	Microsoft C/C++
MRC	mIRC file	mIRC
MRK	Windows User Benchmark	Win95
MRS	Macro Resource file	WordPerfect for Win
MS	Microsoft antivirus report	MSAV
MSC	Microsoft C makefile
MSC	management saved console	Microsoft; Microsoft MMC
MSI	Windows Installer Package	Windows Operating Systems
MSD	Secure and Encrypted File	mysecuredelivery/Download
MSDL	Manchester Scene Description Language
MSG	Message base (e.g. HMB)
MSG	Message text file (ASCII)	Microsoft Outlook
MSG	ZVoice digitized voice file
MSE	Set file	Magic Set Editor
MSO	Microsoft Word OLE Web Page Storage Stream	Microsoft Office
MSO	Microsoft Outlook metadata for a Microsoft Word 2000 email attachment.	Microsoft Outlook
MSP	Bitmap graphics file	Microsoft Paint
MSP	Graphics format	Microsoft Paint
MSPRODUCER	Media Project	Microsoft Producer (for Microsoft PowerPoint XP/2003) Project
MSQM	data	Microsoft Message Queuing
MSN	Project	National Instruments for NI MultiSim-Electronic Circuit simulator
MSS	Manuscript text file	Perfect Writer - Scribble - MINCE - Jove
MST	Document	MS Test
MST	Minispecification file	Prosa
MST	Setup script file	Microsoft Windows SDK
MSW	Text file	Microsoft Word
MSX	CP/M archive	MSX
MTH	Math file	Derive
MTL	Wavefront
MTM	Music format	MultiTracker
MTS	Master Track Pro Files	MTPro 4
MTS	data	F1 2001, F1 2002 and F1 Challenge 1999 - 2002 car physics (All from the EA Sports F1 Series)
MTV	MTV Ray Tracer graphic file
MTW	Datafile	Minitab
MU	Quattro pro for DOS Menu definition file	Quattro Pro
MUS	Finale music document.	Finale
MUS	Music format (MIDI in Doom)
MUS	Sound file	MusicTime
MUZ	Hover Game MIDI File	Windows' Hover! Game
MVF	Stop frame file	AutoCAD AutoFlix
MVI	Movie command file	AutoCAD AutoFlix
MVO	Data	Mad Virgin 3D object
MVW	Log file	Saber LAN
MWF	Animation	ProMotion
MWS	MWave DSP synths instrument	AWAVE
MXF	Material exchange format (RFC 4539, SMPTE 377M)
MXL	PackRat 5.0 support DLLs	PackRat 5.0
MXM	Material	Maxwell Render
MXP	Adobe Extension File	Adobe Dreamweaver and Adobe Flash
MXP	3ds Max Configuration File	3ds Max
MXP	MasterCook exported recipe
MXT	Data	Microsoft C
MYP	Presentation	MM Make Your Point
MZ	Binary-format Map	MazeEdit
MZE	Text-format Map	MazeEdit
MZG	Binary-format Map Collection	MazeEdit
MZX	Binary-format Encrypted Map	MazeEdit

N

Ext.	Description	Used by
NAM	Name Space Modules	Novell NetWare
NAP	Naplps file (VideoShow)	EnerGraphics
NAPLPS	North American Presentation Layer Protocol Syntax
NB	Text file	Nota Bene
NB	Wolfram Mathematica Notebook	Mathematica
NBF	Nokia Backup File	Nokia Mobile Phones
NC	Binary Data	netCDF software package
NC	Instructions for NC (Numerical Control) machine	CAMS
NC	Non-error checking preprosessed Goc source code	Geoworks
NCC	CNC (Computer Numeric Control) control file	CamView 3D
NCD	Norton Change Directory support file	Norton Commander
NCP	Re-volt Collision file	Re-volt
NDB	Network database	Intellicom - Compex
NDS	Nintendo DS ROM file used for Homebrew and commercial (Game) files on DS	Nintendo DS
NDL	Nodelist file
NDX	Index file	dBASE II - III - IV - dBFast
NEO	Raster graphics file	Atari Neochrome
NES	iNES ROM image format
NET	Network configuration/info file
NEU	Pro/Engineer neutral file format	PTC Pro/Engineer
netCDF	Network Common Data Format
NEW	New info
NFF	Haines Neutral File Format
NFF	WorldToolKit Neutral File Format
NFO	Folioview database
NFO	Help format	Nextpage Folio
NFO	Info file	Compact NFO Viewer
NG	Hypertext Database	Norton Guide
NGO	NG linker object file	NGML
NGS ;	NG compiler source file	NGC
NIF	netimmerse/gamebyro file
NIL	NIL	Icon Hear-It
NITF	National Imagery Transmission Format
NK2	e-mail address autocomplete archive	Microsoft Office Outlook
NL	Norton Desktop Icon Library
NLM	Netware loadable module	Novell Netware
NLS	National Language Support file	MS-DOS
NLX	Form	FormWorx 3.0
nmf	Node Map File	Used by SpicyNodes
nnn	Arj archive volumes up to 999	ARJ
nnn	Netware unicode rule table (e.g. 1250_Uni.036)	Novell Netware
nnn	News about smth with ext. of ver. number
nnn	RAR archive volumes up to 999	RAR
NOT	Notation
NOT	Yard Notes File	FYM
NP	Project schedule (Nokia Planner)	Nokia Planner
NPI	Source for DGEN.EXE interpreter	dBASE Application Generator
NPJ	Nile Project	Game Mission Editor
NRG	Nero Disc Image File	Nero Express / Burning ROM
NRW	Nikon Coolpix RAW image	Nikon
NSA	media	Nullsoft Streaming Audio
NSF	database	Lotus Notes
NSF	Music module	NES Sound File
NSS	Norton screensaver module	NC - NDW Screen Saver
NST	Music module	Amiga Noise Tracker
NSV	media	Nullsoft Streaming Video
NSX	Compound index file	SuccessWare SIX 3.00
NT	Startup files	Windows NT
NT3	BAHN Layout file	JBSS BAHN
NTF	database design template	Lotus Notes
NTH	Nokia Theme File	Nokia PC Suite
NTR	Executable ASCII text file (strip header and rename)	netrun31.zip
NTS	Executable ASCII text file (strip header and rename)	netsend1.zip
NTS	Tutorial	Norton
NTX	Database index file	Clipper 5
NUF	Message for new users on their 1st call	Procomm Plus
NUMBERS	Numbers spreadsheet file	Numbers (Apple iWork '08)
NV	NewViews DOS accounting database	QW Page NewViews
NV2	NewViews accounting database	QW Page NewViews
NWS	Info text file (latest news) (ASCII)
NXT	Sound (NeXT format)

O

Ext.	Description	Used by
O$$	Outfile	Sprint
O	Object file	UNIX - Atari - GCC
O01	Typhoon vOice file	AWAVE
OAZ	Fax	NetFax Manager
OB	Object cut/paste file	IBM LinkWay
OBD	Microsoft Office Binder	MSOffice
OBJ	Compiled machine language code
OBJ	Object code	Intel Relocatable Object Module
OBJ	Wavefront Object
OBJF	Data	Triangle strips object
OBR	Object browser data file	Borland C++
OBS	Script	ObjectScript
OBT	Microsoft Office Binder Template	MSOffice
OBV	Visual interface	ObjectScript
OBZ	Microsoft Office Binder Wizard	MSOffice
OCF	Object Craft File	Object Craft
OCD	OCAD Map File	OCAD
OCR	Incoming fax transcribed to text	FAXGrapper
OCT	Musical file	Pctalizer
OCX	New Custom Control's format in VB 4.0	Visual Basic
OCX	OLE custom control
ODB	OpenDocument database	OpenOffice.org Base
ODF	OpenDocument formula	OpenOffice.org Math
ODG	OpenDocument drawing	OpenOffice.org Draw
ODIF	Open Document Interchange Format
ODL	Object Description Language
ODL	Type library source	Visual C++
ODM	OpenDocument master document	OpenOffice.org Writer
ODP	OpenDocument presentation	OpenOffice.org Impress
ODS	OpenDocument spreadsheet	OpenOffice.org Calc
ODT	OpenDocument text document	OpenOffice.org Writer
OFD	Form definition	ObjectView
OFF	Object File Format vector graphics file
OFF	Object File Format vector graphics
OFM	PostScript font description file
OFN	Microsoft Office documents	Microsoft Office
OGG	Ogg multimedia container format
OHB	Source	On Hand Basic
OHS	Outbound History	Bink/+
OIF	QuickBase file format
OKT	Music (8 channels)	Oktalyzer
OKT	Music format	Oktalyzer
OLB	Object library	VAX
OLD	Backup file
OLI	Text file	Olivetti
OLSR	Configuration file	olsrd
OMA	Audio file	Labelgate CD 2, MAGIQLIP2
OMG	Audio file	Sony compressed audio file (ATRAC3)
OMF	Open Media Framework	Avid Media Composer
OOF	Data	Outrage 3D Object Format (Descent)
OOG	Data	WEBOOGL 3D object
OOM	Swap file	Shroom
OPJ	Origin Project File	Origin version 4.1 and later
OPN	Active options	Exact
OPT	Options	name used by many programs for configuration information
OPT	Delphi project options	Borland Delphi
OPT	Optimize support file	QEMM
OPW	Organization chart	Org Plus for Windows
OPX	Inactive options	Exact
ORA	Parameter file	Oracle
ORC	Orchestra MIDI file	CSound
ORG	Calendar file	Lotus Organizer
ORG	Older Origin Project	Origin versions 4 or earlier
OTG	OpenDocument drawing template	OpenOffice.org Draw
OTB	Over-the-air bitmap graphics
OTF	Subtitle font information for media content	Media players / software which support PGS subtitling
OTH	OpenDocument HTML document template	OpenOffice.org
OTL	Outline font description	Z-Soft Type Foundry
OTL	Ventura Publisher's Type Foundry Outline Editor format
OTP	OpenDocument presentation template	OpenOffice.org Impress
OTS	OpenDocument spreadsheet template	OpenOffice.org Math
OTT	OpenDocument text document template	OpenOffice.org Writer
OTX	Text file	Olivetti Olitext Plus
OUT	Output file
OUT	Design II for Windows Output file
OV1	Overlay file (part of program to be loaded when needed)
OV2	Overlay file (part of program to be loaded when needed)	TomTom Point of Interest
OVD	Datafile	ObjectVision
OVL	Overlay file (part of program to be loaded when needed)
OVR	Overlay file (part of program to be loaded when needed)
OXT	OpenOffice.org extension	OpenOffice.org

P

Ext.	Description	Used by
P	Database PROGRESS source code	PROGRESS
P	PASCAL source code file
P	Parser source code file
P	Picture file	APPLAUSE
P	Rea-C-Time application parameter file	ReaGeniX code generator
P0?	Split archive UC2	SAS.EXE
P10	Tektronix Plot	GCGW
P10	Certificate Request
P12	Personal Information Exchange	"Crypto Shell Extensions"
P16	Music (16 channels)	ProTracker Studio 16
P22	Patch file (Patch22)	Patch22
P80	PLM-80 source
P86	PLM-86 source
p2v	Backupfile of a project in eventplanning software plan2viz (windowsbased)
P3T	PlayStation 3 Theme file	PS3 Theme settings menu
PA1	Worktable	PageAhead
PAC	SBStudio II Package or Song	SBStudio II
PAC	STAD Image (graphics ?)
PACK
PACKAGE	Contents	The Sims 2 - Spore - The Sims 3
PAD	Automatic print definitions	Produa
PAD	Keypad definition	Telemate
PAF	For Personal Ancestral File data files
PAGES	Pages document file	Pages (Apple iWork '08)
PAK	Archive	Pak
PAL	Palette file	Microsoft Draw - Win. Paintbrush - many
PAL	Palette file	Diablo II
PAN	Printer-specific file (copy to coreldrw.ink)	CorelDRAW
PAR	Parameter file	Fractint
PAR	PARTS application	Digitalk PARTS
PAR	Permanent output file	Windows 3.x
PAR	Parity Archive
PAR2	Parity Archive v2
PART	Part of a download file
PAS	Pascal language source	Borland Pascal
PAT	Gravis Ultrasound Patch	Convert (c) Villena
PAT	Hatch patterns	AutoCAD - Photostyler
PAT	Vector fill files	CorelDRAW
PAT	Pattern File	Photoshop
PAT	GIMP pattern
PB	Fax	FAXability Plus
PB	Phonebook	WinFax Pro
PB	Proboard Conf. files	Proboard
PB	Setup file	PixBase
PB1	Document	First Publisher for Windows
PBA	Powerbasic BASIC source code	Genus
PBD	Phone book	FaxNOW! - Faxit
PBD	Molecule (protein data bank)
PBI	Powerbasic include file	Genus
PBI	Profiler Binary Input	Microsoft Source Profiler
PBK	Microsoft Network Phone book	MSN
PBL	Powerbasic library	Genus
PBLIB	Power Library	PowerBASIC
PBM	PBM Portable Bit Map graphics format	Jasc Media C.
PBM	Planar bitmap graphics	XLib
PBO	Profiler Binary Output	Microsoft Source Profiler
PBT	Profiler Binary Table	Microsoft Source Profiler
PC	Text file containing IBM PC specific info
PC3	Custom palette	Harvard Graphics 3.0
PC8	ASCII text IBM8 character set	NewWave Write
PCA	Perfect Clarity Audio	Sony Vegas Pro
PCB	P-CAD database	P-CAD, PCBExpress, and other Printed Curcuit Board design software
PCB	Artwork design file (Circuit board design)	Zuken CadStar
PCC	Cutout picture vector graphics	PC Paintbrush
PCD	Graphics format (Kodak Photo-CD)
PCD	Kodak Photo-CD Image graphics file (768x512)	hpcdtoppm
PCF	Pixel Coordination Format
PCH	Patch file
PCH	Precompiled header	Microsoft C/C++
PCJ	Multimedia authoring tool graphics file	IBM's Linkaway-Live
PCK	Pickfile	Turbo Pascal
PCL	HP-PCL graphics data file	HP Printer Control Language
PCM	OKI MSM6376 synth chip PCM	AWAVE
PCM	PCM	Authorware
PCS	Microsoft PowerPoint picture package	Microsoft PowerPoint - Microsoft ClipArt Gallery
PCS	PCSurvey file	PCSurvey by Softart - Land Surveying Software
PCT	Bitmap graphics file	Macintosh b&w PICT1 - color PICT2
PCW	Text file	PC Write
PCX	PC paintbrush bitmap format	QPeg - Display - ZSoft - PC Paintbrush
PDA	Bitmap graphics
PDB	Packrat 5.0 data file	Packrat 5.0
PDB	container format (envelope) for Palm OS databases	Palm OS, Garnet OS, Access Linux Platform, e-book
PDB	debugging data	Microsoft Windows
PDB	Molecule (protein data bank)
PDD	Adobe Photoshop Elements Image	Adobe Photoshop Elements
PDE	Pathology Data Exchange
PDE	data	PowerDesk Encrypted
PDF	Adobe's Portable Document Format	Adobe Acrobat Reader
PDF	Graphics file (ED-SCAN 24bit format)
PDF	Package Definition File
PDF	PCAD Database Interchange Format	Pdifin.exe - Pdifout.exe
PDF	Print device information Netware
PDG	Print Shop Deluxe data file
PDI	Portable Database Image
PDL	Project Description Language file	Borland C++ 4.5
PDM	Program	Deskmate
PDM	PowerDesigner's physical data model (relational model) file format	PowerDesigner
PDM	Visual Basic (VB) Project Information File	Visual Basic
PDN	Image file	Paint.NET
PDS	PALASM Design Description
PDS	Pds graphics
PDS	Planetary Data System Format
PDS	Pldasm source code file (hardware assembly)
PDV	Printer driver	Paintbrush
PDW	Document	Professional Draw
PEB	Program Editor bottom overflow file	WordPerfect Library
PED	Program Editor delete save	WordPerfect Library
PEM	Program Editor macro	WordPerfect Library
PEQ	Program Editor print queue file	WordPerfect Library
PER	Program Editor resident area	WordPerfect Library
PES	Program Editor work space file	WordPerfect Library
PET	Program Editor top overflow file	WordPerfect Library
pet	package	Puppy Linux
PEX	Proboard EXecutable file (Executed from PB)	Proboard
PFA	PostScript Font File
PFA	Type 3 font file (unhinted PostScript font)
PFB	Adobe Acrobat document	Adobe Acrobat Reader
PFB	PostScript font	Adobe Type Manager (ATM)
PFC	(Personal File Cabinet) contains e-mail, preferences and other personal information	AOL
PFC	Text file	First Choice
PFK	Programmable function keys	XTreePro
PFM	Windows Type 1 font metric file
PFS	Database (PFS:FILE) - text file (PFS:Write)	PFS
PFT	Printer font	ChiWriter
PG	Page cut/paste file	IBM LinkWay
PGD		PGP cripted disk
PGI	Printer Graphics File device driver	PGRAPH library
PGL	HP Plotter vector graphics format
PGM	Graphics format (Portable GrayMap)	JASC Media C.
PGM	Program	Signature
PGP	Support file	Pretty Good Privacy RSA System
PGS	Manual page	man4dos
PH	Optimized .goh file	Geoworks
PH	Perl header file
PH	Phrase-table	Microsoft C/C++
PHD	PolyHedra Database
PHM	Phone book	DN - Lync
PHN	Phone list	UltraFax - QmodemPro
PHO	Phone database	Metz Phone for Windows
PHP	PHP file
PHP3	PHP 3 file
PHP4	PHP 4 file
PHF	Database File	Nuverb Systems Inc: Donarius
PHR	Phrases	LocoScript
PI2	Portrait Innovations High Resolution Encrypted Image file	Portrait Innovations Studio2 (proprietary)
PIC	123 Vector graphics format	CShow - Alchemy - Paint (Pictor)
PIC	Bitmap graphics file	Macintosh b&w PICT1 - color PICT2
PIC	Lotus picture
PIC	PIXAR picture file	SDSC Image Tool
PICT	Macintosh Picture
PIE	GlovePIE script file	GlovePIE
PIF	OS/2 graphics metafile	PICVIEW.EXE
PIF	Program Information File	Windows 3.x
PIF	Vector graphics GDF format file (IBM mainframe computers)
PiM	Pascal Text Mode Image File	The Ultimate Draw
PIT	Compressed Mac file archive created by PACKIT	unpackit.zoo
PIV	Pivot Stick Animator file	Pivot Stick Animator
PIX	Alias image file	SDSC Image Tool
PIX	Inset Pix
PJ	Project	CA-SuperProject
PJT	Additional (FPT) project description file	FoxPro
PJX	Main (DBF) project description file	FoxPro
PK	PacKed bitmap font bitmap file (TeX DVI drivers)
PK	Peak file	Cool Edit
PK2	Quake 2 data file	id Software
PK3	Quake 3 data file	id Software
PK4	Doom 3 and Quake 4 data file	id Software
PKA	Archive	PKARC
PKG	Installer script	Next, Mac OS X, Sony PS3
PKG	P-CAD database	P-CAD
PKT	Fido message packet	FTN software
PL	Palette	Harvard Graphics
PL	Perl source code file
PL	Prolog source code file
PL	Property List font metric file	TeX
PL1	Room plan	3D Home Architect
PL2	Palette	Diablo II
PL3	Chart palette	Harvard Graphics 3.0
PLA	Playlist
PLB	FoxPro library	FoxPro
PLB	P-CAD library	P-CAD
PLC	Add-in file (functions - macros - applications)	Lotus 1-2-3
PLC	P-CAD database	P-CAD
PLD	PhotoLine Document	PhotoLine image processing
PLE	Encrypted Chat Log	Messenger Plus! Live Plugin - Log viewer
PLIST	Mac OS Property List, also used on iOS, NeXTSTEP, and GNUstep	Apple's Property List Editor
PLL	Prelinked library	CA Clipper
PLM	DisorderTracker2 music module	AWAVE
PLN	Spreadsheet	WordPerfect for Win
PLP	Playlist
PLP	Messenger Plus! Sound Pack	Messenger Plus! Live Plugin
PLS	Playlist file	WarpVision (OS/2)
PLSC	Messenger Plus! Script Pack	Messenger Plus! Live Plugin
PLSK	Messenger Plus! Skin Pack	Messenger Plus! Live Plugin
PLT	HPGL plotter file vector graphics	AutoCAD
PLT	Output file for ploter
PLT	P CAD: Output file editor for PCPLOT or PCPRINT	P CAD
PLT	Page Magic 2.0 paper format	Page Magic 2.0
PLT	Palette
PLT	Table for .pll	CA Clipper
PLY	Data	PopMail
PLY	Presentation screen	Harvard Spotlight
PLY2	Data	PLY2 object
PLY	ZipPack
PM	Auran Jet progressive mesh file (obsoleted by IM and LM)	Trainz
PM	Perl module
PM	Bitmap graphics	Presentation Manager
PM3	PageMaker 3.0 data file	PageMaker 3.0
PM4	Document	PageMaker 4
PM5	Aldus PageMaker 5.0 publication	Aldus PageMaker
PMC	Graphics	A4TECH Scanner
PMI	OS/2 V3 SVGA PMI-File	Svga.exe
PMI	PhatPad note	PathWare
PMM	Program file	Amaris BTX/2
PMP	PhotoMorph Project	PhotoMorph
PN3	Printer device driver	Harvard Graphics 3.0
PNG	Portable Network Graphics
PNF	Pre-compiled Setup Information file	Microsoft Windows
PNM	PBM Portable aNy Map graphics file
PNT	Macintosh painting
PNT	Pointlist segment	FTN software
PNT	QWK reader pointer file	MarkMail 2.x
POF	Altera FPGA programming file (External Flash)	Altera Quartus
POH	Optimized .goh file	Geoworks
POL	InnovMetric Software Polygon Models Format
POLICY	Group Policy File	Microsoft Windows
POLY	Data	Patrick Flynn's Poly Format - 3D object
POP	Messages index	PopMail
POP	Pop-up menu object	dBASE Application Generator
POT	Microsoft PowerPoint template
POV	Raytraced graphics image	Persistence Of Vision
POW	Power Chords instrument/song file	Power Chords
PP	Amiga archive	POWERPACKER
PPA	Microsoft PowerPoint Add-in
PPB	Button bar for Print Preview	WordPerfect for Win
PPD	PostScript printer description file
PPJ	Premiere Project	Premiere
PPK	Archive (using for many distributives)	PPK
PPL	PolaroidPalettePlus ColorKey device driver	Harvard Graphics 3.0
PPM	Graphics format (Portable PixelMap)	JASC Media C.
PPO	Preprocessor output	CA Clipper 5.*
PPP	Publication	PagePlus
PPS	Storyboard	Personal Producer
PPS	Microsoft PowerPoint Slideshow (stand alone slideshow)
PPT	Microsoft PowerPoint Presentation	Microsoft PowerPoint
PPTX	Office Open XML Presentation
PR1	Packrat 4.0 data file	Packrat 4.0
PR2	Packrat 4.x data file	Packrat 4.x
PR2	Presentation	Aldus Persuasion 2.x
PR2	Printer driver	dBASE IV
PR3	PostScript printer driver	dBASE IV
PR3	Presentation	Aldus Persuasion 3.x
PRC	container format (envelope) for Palm OS databases	Palm OS, Garnet OS, Access Linux Platform, Mobipocket
PRC	"Product Representation Compact", for embedding 3D data in a PDF file	CAE and CAM applications
PRD	Printer driver
PRE	Presentation	Freelance Graphics
PRE	Settings	Programmer's WorkBench, Microsoft C/C++
PRE	Stork graphic file
PRF	CheckIt Pro v1.0 data file	CheckIt Pro 1.0
PRF	Pixel Run Format graphics file	Improces - Fastgraph
PRF	Printer driver	dBASE IV
PRF	Profiler output
PRG	Program source code (e.g. Clipper language)	CA Clipper
PRG	Program source	dBASE IV - FoxPro - Clipper 5 - dBFast
PRG	Program	Atari
PRI	Printer definitions	LocoScript
PRJ	Borland C++ IDE project file	BC.EXE - BCW.EXE
PRK	SimPark Saved File	SimPark
PRM	Parameters
PRN	Printer driver	Signature
PRN	Text file	Lotus 1-2-3 - Symphony
PRN	Usually printer output file
PRO	Profile	used by many programs to store configuration data
PRO	Graphics profile file	DOS
PRO	Proboard conf. file	Proboard
PRO	Prolog language source
PRO	PROLOG source code file
PROJ	Project File (Interface Builder)	NeXT
PROPERTIES	Java properties file	Java applications
PROTO	Message specification	Google Protocol Buffers
PRR	The Perfect Resume data file	Perfect Resume
PRS	Norton Viewer DLL file
PRS	Presentation	Harvard Graphics Win
PRS	Printer Resource e.g. fonts	WordPerfect for Win
PRS	Procedure	dBASE IV
PRT	P-CAD component	P-CAD
PRT	Part or Drawing	Cadkey
PRT	Printer driver	Dr. Halo
PRX	Compiled program	FoxPro
PS	Document in PostScript format	adobe
PSA	Archive (Pretty Simple Archive)	PSA.OUT (GNU)
PSB	For big Photoshop files	Photoshop Document
PSD	Design II for Windows Process Simulation Diagram
PSD	Periscope Debbuger Def file	Periscope
PSD	Photoshop bitmap file	Photoshop document
PSE	see PSEG
PSEG	Bitmap graphics	IBM printer Page SEgment
PSF	Outline PostScript printer font	ChiWriter
PSM	Music format (Protracker Studio Module)	Protracker - MASI
PSM	Symbol table of IDE	Turbo Pascal
PSM	3D Model	18 Wheels Of Steel
PSN	Presentation file for Sound Script	Win
PSP	image file with layers	Paint Shop Pro (all versions)
PSQ	Premiere Sequence	Premiere
PST	Postbox file	BMail
PST	Archive File	Microsoft Outlook
PSV	PlayStation 2/PlayStation 3 saved game	PlayStation 2 and PlayStation 3
PSW	File w/ passwords for any program/game	many
PT	Game crack	Player Tools
PT	Kodak Precition Color Management System
PT3	Device driver	Harvard Graphics 3.0
PT3	Template	PageMaker 3
PT4	Template	PageMaker 4
PT5	Aldus PageMaker 5.0 publication template	Aldus PageMaker
PTB	Power Tab Software	Power Tab Editor
PTB	Script	PubTech BatchWorks
PTF	PlayStation Portable Theme file	PSP Theme settings menu
PTF	ProTools Session File	Digidesign ProTools
PTG	Panasonic Title Graphics
PTL	Premiere Title	Premiere
PTM	Macro	PubTech BatchWorks
PTM	Music format
PTM	Page Magic 2.0 template	Page Magic 2.0
PTN	Pattern	Cadkey
PTN	Pattern	CarveWright/CompuCarve Designer
PTR	OS/2 cursor image file	ICONEDIT.EXE
PTR	QWK reader pointer file	QMail
PTU	Performer Terrain Utilities
PUB	Package File	Exstream Dialogue
PUB	Page template	Microsoft Publisher
PUB	Public key ring file	Pretty Good Privacy RSA System
PUB	Publication	Ventura Publisher - 1st Publisher
PUD	Warcraft II Map file	Warcraft II
PUT	Archive	PUT
PUT	Graphics format	WScan
PVD	Script	Instalit
PVL	Library	Instalit
PVM	Texture Files	PVMEdit
PVT	Local Fidonet pointlist	FTN software
PW	Text file	Professional Write
PWF	Workflow Files	Mac OS X Server Podcast Producer
PWK	Workspace File	PolyWorks
PWL	Password List
PWP	Text document	Professional WritePlus
PX	Paradox 3.0 file	Paradox 3.0
PXP	3DS Process file	3D Studio
PXR	Pixiar Picio	AltamiraComposer
PXZ	Compressed file to exchange media elements	PSALMO
PY	Python script file	Python interpreter
PYC	Compiled Python module	Python interpreter
PYI	Cognos Powerplay Model
PYO	Optimized compiled Python module	Python interpreter
PZD	Default settings	Pizazz Plus
PZI	Graphics format	PZP
PZO	Overlay file	Pizazz Plus
PZP	Palette	Pizazz Plus
PZS	Settings	Pizazz Plus
PZT	Transfer file	Pizazz Plus
PZX	Swap file	Pizazz Plus

Q

Ext.	Description	Used by
Q0	Q0 graphic file
Q3S	Data	Quick3D Scene
QAG	Quick Access Group	Norton Desktop
QAP	Application	Omnis Quartz - Omnis Studio
QB	Tony Hawk's Pro Skater series scripting files
QBB	Quickbooks Backup File
QBE	Saved query (Query By Example)	dBASE IV - Quattro Pro
QBO	Compiled query	dBASE IV
QBW	Spreadsheet	QuickBooks for Windows
QCH	Qt Compressed Help	Trolltech Qt Assistant
QCP	Mp3 extension on Motorola ringtones	Motorola Phones
QDF	Data file	Quicken data file
QDK	Backup of startup files created by Optimize	QEMM
QDn	Data file - segment n	Omnis Quartz- Omnis Studio
QDV	Graphics file	Steve Blackstock Giffer
QDR	Configuration file	Q-Dir
QEF	Query file	Q+E for Microsoft Excel
QFX	Quicken-specific implementation of the OFX specification	Intuit Quicken
QFX	Fax	QuickLink
QG3	Data	QuickMem Greek
QHC	Qt Help Collection	Trolltech Qt Assistant
QHCP	Qt Help Collection Project	Trolltech Qt Assistant
QHP	Qt Help Project	Trolltech Qt Assistant
QIF	Quicken Interchange Format	Intuit Quicken
QIZ	World book quiz	World Book
QLB	Quick library	Microsoft C/C++
QLC	ATM Type 1 fonts script	Adobe Type Manager
QLP	Printer driver	QuickLink
QM4	Options or services file	QMail 4.x Mail Door
QPR	Generated query program	FoxPro
QPR	Print queue device driver	OS/2
QPX	Compiled executable QBE query file	FoxPro
QRS	Equation Editor support file	WordPerfect for Win
QRT	Graphics format (QRT ray tracing)
QRY	Query	dBASE IV
QT	QuickTime movie (animation)
QTVR	QuickTime VR Movie
QUOX	Question Object Document	Quobject Designer and Quobject Explorer
QVD	QlikView Document (Data)	QlikView Compressed Database File
QVW	QlikView Document (View)	QlikView Presentation File
QWK	QWK reader message file
QXD	Document	QuarkXPress
QXL	Element library	QuarkXPress

R

Ext.	Description	Used by
R	Ratfor file
R	Script file	R
R00, R01, ...	Part of a multi-file RAR archive.
R2D	Reflex 2 datafile	Reflex 2
R3D	Red Raw Video (raw video data created with a Red camera)	Red Camera
R8	Raw graphics file (one byte per pixel) plane one	PicLab
R8P	PCL 4 bitmap font file	Intellifont
RA	Remote Access conf. files	RA
RA0, RA1, ...	Part of a multi-file RAR archive.
RAD	2-op FM music	Reality AdLib Tracker
RAD	Radiance
RAL	Remote Access Language file	Remote Access
RAM	Ramfile	RealAudio
RAR	Archive	RAR
RAS	Graphics format	SUN Raster
RAT	Datafile (RATS)
RAW	HSI raw graphic file
RAW	PCM Signed Raw Sound File
RAW	QRT graphic file
RAY	Rayshade
RB	Ruby Script file
RBF	Datafile	Rbase
RBLX	ROBLOX model	ROBLOX
RC	Configuration file	emacs
RC	Resource Compiler script file	Microsoft C/C++, Borland C++
RC	Resource Script	Resource Writer
RC	UUPC configuration files	UUPC
RC	Windows resource compiler script	RC.EXE -Resource WorkShop - OS/2
RCG	Netscape newsgroup file (netsc.rcg)
RData	Data file	R
RDF	Compiled UIC source code	Geoworks UI Compiler
RDI	Device-independent bitmap file (RIFF RDIB format)
RDP	RDP connection	Remote Desktop connection
RDX	Datafile	Reflex
REC	Archivation protocol	ARCSERVE
REC	Datafile	EpiInfo
REC	Record file	Sprint
REC	Windows Recorder Macro File	WinRecorder
RED	Path info	Clarion Modula-2
RED	REDuced nodelist file	T-Mail nodelist Compiler
REF	Cross-reference
REG	OLE Registration file	Windows 3.x
REG	Registration information or key
REL	Foreground job relocatable file	RT-11
REM	Remarks definition	Sourcer
REM	Remarks
REP	QWK reader reply file
REP	Report file used by many applications
REP	Report	Report Designer - CodeReporter - DataBoss
REQ	File request	FTN Software
RES	Compiled resource	Microsoft C/C++, Borland C++
RES	DBASE resources	dBASE IV
RES	Windows compiled resource package	Win
REV	Revision file	Geoworks
REX	PharLab executable file (old format)	PharLab
REX	Report definition	Oracle
REX	Rexx language source file	Rexx
REZ	Resource file
RF	Sun raster graphics file
RFM	Report ForMat (script for customized report)	Nuverb Systems Inc: Donarius
RFT	DCA/RFT Revisable Format Text file	IBM DisplayWrite 4.0-5.1
RGB	SGI RGB image file (RAW)	SDSC Image Tool
RGX	Symbol tables etc. info	ReaGeniX code generator
RH	Resource header file	Borland C++ 4.5
RH	Windows resource file header	RC.EXE
RHistory	Command history logfile	R
RI	Data	Lotus 1-2-3
RIB	Graphics (Renderman Interface Bytestream)	3D Reality
RIC	Fax	Ricoh
RIF	RIFF bitmap graphics (Resource Interchange File Format)	Fractal Design Painter
RIP	TeleGrafix Remote Imaging Protocol	Maximus 3.0
RIX	Graphics (ColoRIX Image File)	ColoRIX
RL4	Bitmap graphics
RL8	Bitmap graphics
RLA	Wavefront raster image file	SDSC Image Tool
RLB	Data hgw.rlb	Harvard Graphics Win
RLC	Graphics 1bit/pixel scanner output
RLD	Norton Commander 5.0 temp file	NC 5.0
RLD	OSIMapDef. RecLoad Definition
RLE	Utah Run Length Encoded rasterfile graphic file	SDSC Image Tool
RLZ	REALIZER source code file	CA-Realizer
RM	Real Media	Real Player
RMB	data	RegistryMaster
RMI	Windows alternate synthesized sound format	RIFF RMID format
RMK	Make file	CA Clipper - RMAKE
RMVB	Real Media Variable Bitrate	Real player
RN	XPL program for Nota Bene users
RNA	lime Network Real Native Application File	All lime Network Applications
RND	Rendering Slide	AutoCAD AutoShade
Rnn	Multi volume RAR archive	RAR
RNO	Runoff file	VAX
ROL	FM music Adlib Music File	Roland
ROM	Read Only Memory image in emulators, AONs, etc.
ROO	CODASYL DBMS Database Root	Oracle
RPB	Data report file used by CP Backup	CP Backup
RPD	Database	RapidFile
RPF	AutoCAD pattern	ACAD
RPL	Text document	Replica
RPM	Red Hat Package Manager	Red Hat Linux
RPT	Report file used by many applications
RRD	Reduced Resolution Dataset	ESRI (GIS)
RS	Data file	Amiga Resource - Reassembler
RS	Rust language source
RS_	Resource fork of a Macintosh file	Mac-ette
RSC	Resource file	ViewMax - many
RSL	Application - Project	resolver one
RSL	Resource Library used by PC Tools for Windows	PC Tools - Win
RSP	Response file (text file containing input expected by e.g. LINK)
RSP	Response File	OS/2
RSY	FLEXIT Multishot Survey Raw Data file	FLEXIT
RTF	Rich Text Format text file (help file script)	many - Microsoft Word
RTFD	RTF-Packet	NeXT
RTL	HP RTL graphic file
RTL	Run-Time library	Norton Utilities
RTL	Text file
RTP	RTPatch software update package data file	Pocket soft patch
RTS	Realizer executable file
RTS	Runtime library file	CA-Realizer
RUL	Echo-conference rules
RUN	PC Tools for Windows batch file	PC Tools
RUNZ	pseudo-executable file, used in Portable Apps and software installers for Super OS	RUNZ Framework
RUS	Russian text
RV	Mobile pricelist data file	Mobile
RVF		TRichView
RVW	Review
RWS	Borland Resource Workshop symbol file	Resource Workshop
RWS	Resource Workshop data file	Borland C++
RWX	Criterion RenderWare
RWX	MEME Shape File
RWX	Script	RenderWare
RWZ	Microsoft Outlook Rules Wizard File	Microsoft Outlook
RXD	Reflex 1 datafile	Reflex 1
RZK	File Crypt password file	All text editors
RZX	File Crypt encrypted file	File Crypt (Akte Krypta, Kriptirnik)

S

Ext.	Description	Used by
S$$	Temporary sort file	Sprint
S	ASSEMBLY source code file	unix
S	Multi Edit macro file source	Multi Edit
S	MSTS Shape file	MSTS
S19	Motorola ASCII format of executables
S1K	S1000 Simnet Format
S3I	Digiplayer/ST3 Sample File	Digiplayer - ST3
S3M	Music (16 channels)	Scream Tracker 3.0 - DMP
S7I	Seed7 library / include file	Seed7 interpreter and compiler
SA?	Packed mail	FTN software
SAB	Saber file	Star Wars: Jedi Knight Jedi Academy
SAF	see SAIF
SAFE	SafeIT Encrypted
SAIF	Spatial Archive Interchange Format
SAL	Datafile	SORITEC
SAN	LucasArts' SMUSH/INSANE animation
SAM	Ami Pro data file	Ami Pro
SAM	Text file	Samna - Lotus Ami/Ami Pro
SAP	Atari SAP music format.
SAR	Archive	SAR
SAT	ACIS
SATS	Static source	ATS
SAV	Backup file (saved file)
SAV	Configuration
SAV	Executable	RT-11
SAV	SPSS "System File"	PSPP
SAV	Saved game state	Spider Solitaire (Windows)
SAVER	Screensaver	Mac OS X
SB	Audio file (signed byte)
SB	Raw Signed Byte (8bit) data	AWAVE
SB	Raw Signed PCM Byte 8bit data	AWAVE
SB	Scratch project	Scratch
SBD	Storyboard	Storyboard Editor
SBH	Header	ScriptBasic
SBI	Sound Blaster Instrument file (Creative Labs)
SBK	Emu SoundFont Bank (AWE32 Bank)	Convert (c) Villena
SBL	Stony Brook Pascal library	SB Pascal
SBP	DML program	Superbase 4
SBR	Support file	Source Browser
SBT	Notes related to record	Suberbase 4 Windows
SC	Display driver	Framework II
SC	PAL script	Paradox
SC	Script	Borland Paradox
SC3	Renamed dBASE III screen mask file	dBASE IV
SC3	Screen device driver	Harvard Graphics 3.0
SC3	Saved City	SimCity 3000
SC4	Saved City	SimCity 4
SC4	Game Scenario	RollerCoaster Tycoon Deluxe/Expansion Pack
SC6	Game Scenario	RollerCoaster Tycoon 2
SCA	Datafile	SCA
SCC	Text file
SCD	SCODOL film recorder (Scan Conversion Object Description Language)	SCODOL
SCF	Standard Chromatogram Format	DNA Baser Assembler
SCF	Standard Chromatogram Format	Staden package
SCF	?	SimAnt or SimTown ??
SCF	Windows Explorer Command (e.g.: show desktop.scf)	Windows Explorer
SCF	Multimedia show	ScoreMaker
SCF	Spelling checker configuration file	Symphony
SCH	Project schedule	Schedule Publisher
SCH	Circuit Design Schematic	P-CAD - Orcad - Protel
SchDoc	Circuit Design Schematic	Protel - Altium Designer
SCI	Fax	SciFax
SCI	System Configuration Information
SCM	Scheme source code file
SCM	Schematic file (Circuit Diagram for PCB design)	Zuken CadStar
SCM	StarCraft mission
SCN	SCeNe RTrace
SCN	Screen file	Kermit
SCO	High score
SCP	Script	BITCOM
SCR	Any other screen system
SCR	DEBUG source code file	DOS Debug
SCR	Forth screen (source) file	Forth
SCR	Screen - screen snapshot	dBASE IV - Procomm Plus
SCR	Screen font	LocoScript
SCR	Screen saver	Windows 3.x
SCR	Screen snapshop
SCR	Script file source	TeleMate - Kermit - 1st Reader
SCT	Additional (FPT) screen description file	FoxPro
SCTOR	Raster graphics format used by some very obscure custom operating systems.
SCX	Chart	Stanford Chart
SCX	Graphics format	ColoRIX
SCX	Main (DBF) screen description file	FoxPro
SCX	StarCraft: Brood War scenario	StarCraft: Brood War
SCY	Security file	ReaGeniX
SD	Sound Designer I audio file	AWAVE
SD7	Seed7 source file	Seed7 interpreter and compiler
SDA	Fidonet's Software Distribution Network file archive description
SDC	Video	DigimaxMaster - Samsung NV3
SDC	Synopsys Design Constraints	Electronic Design Automation Tools
SDF	Microsoft SQL Server Compact Edition database file
SDF	Flight data	microdrones GmbH
SDF	Source definition file	Sourcer
SDF	System Data Format file (fixed length ASCII text)
SDI	Software Distribution Network Info file
SDK	Roland S-550/S-50/W-30 Disk Image
SDL	Alias Wavefront Scene Description Language
SDM	Signed Differential Mapping brain maps and/or distributions	Signed Differential Mapping
SDML	Spacial Data Modeling Language
SDN	Software Distribution Network compressd file archive	pak251.exe
SDR	SmartDraw File	SmartDraw Pro
SDS	MIDI Sample DUMP Standard File
SDS	Self Defining Structure provides for N-dimensional very large datasets using HHCode	geographic information systems and relational database management systems
SDTS	Spatial Data Transfer Standard
SDW	Ami Draw Symbol File
SDX	Sample DUMP Exchange File
SEA	Self-Extracting compressed Macintosh file Archive
SEC	compressed file
SEC	Diskreet encrypted file	Diskreet
SEC	Secret key ring file	Pretty Good Privacy RSA System
SEC	Secured animation file	Disney Animation Studio
SED	Self extraction directive file	IExpress
SEN	Scifer Archive Format (Internal Header Mode)
SEP	Printer separator page
SEQ	ABI Text Sequence	Applied Biosystems
SEQ	Atari animation file
SEQ	Video	Tiertex video sequence
SEQ	Sequential Instruction File	Bubble Chamber
SES	Session info	Clarion Modula-2
SES	Multitrack Audio Session info	Adobe Audition
SET	Configuration file	1st Reader
SET	Driver sets created by Install	Symphony
SET	Extension used by Norton Backup and CPS Backup for setup info	Norton Backup - CPS Backup
SET	Hump Assignments File	FYM
SET	Setup options file
SET	YVD card set file	YVD
SF	IRCAM Sound File	CSound package - MixView sound sample editor
SF	JAR Digital Signature
SF	WPS attribute storage (OS/2 WorkPlace Shell) wp_root.sf	OS/2 WorkPlace Shell
SF2	Emu SoundFont Bank v2.0 file	AWAVE
SFB	HP Soft font (obsolete under Windows)
SFD	SoundStage Data file	AWAVE
SFF	Standard Flowgram Format	DNA Baser SFF Workbench tool
SFF	Scene File Format
SFI	Graphics	SIS Framegrabber
SFI	Printer font (HP LaserJet landscape)	Ventura Publisher
SFL	PCL 4 bitmap font (landscape)	landscape - Intellifont - Ventura Publisher
SFL	Sound file	Sound Forge and ACID Pro
SFN	Font	SPX
SFO	Bitstream font file - fontware format
SFP	PCL 4 bitmap font	portrait - Intellifont - Ventura Publisher
SFR	Sonic Foundry Sample Resource	AWAVE
SFS	PCL 5 scalable font file	Intellifont
SFT	Screen font	ChiWriter
SFX	SFX (self-extracting archives) script	RAR
SG1	Graphics	Stanford Graphics
SGF	Document with graphics	Starwriter
SGI	Graphics file	IRIS - Silicon Graphics
SGP	Statistics	STATGRAPHICS Plus
SGT	Save/get keyboard macro	Signature
SH	ASCII archive	SHAR
SH	Unix shell script
SH3	Presentation	Harvard Graphics 3.0
SHAR	Archive	UNSHAR (Unix)
SHB	Background	CorelShow
SHG	Segmented Hyper Graphics	Microsoft's shed.exe, JGsoft's Hotspot Builder, EC Software's Help and Manual
SHK	Apple II archive	SHRINKIT
SHM	Shell macro	WordPerfect Library
SHP	Shape file and source file for text fonts ESRI shapefile	AutoCAD ArcGIS
SHR	see SHAR
SHT	HTML format for WWW	NetScape
SHW	Presentation	Harvard Graphics 2.0 - CorelShow
SHW	Slide show	WordPerfect Presentations
SHX	Shape entities ESRI shapefile	AutoCAD ArcGIS
SIB	Sibelius file	Sibelius 1-5
SIF	Setup Installation Files info	Windows NT Setup
SIG	Current program settings	Signature
SIG	Signature file	ThunderByte AntiVirus - PopMail
SIK	Backup file (Sicherungskopie)	Microsoft Word
SIM	Simon document file - Simon instruction software editor
SIS	symbian file
SIT	Archive (Macintosh)	STUFFIT
SKP	Google SketchUp file
SKY	SYLK Spreadsheet file (used by Multiplan)
SL	S-Lang source code file
SLB	P-CAD library (symbols)	P-CAD
SLB	Slide library	AutoCAD
SLC	SALT (script from Telix) compiled code	Telix
SLD	Slide	AutoCAD
SLDPRT	Part	SolidWorks
SLDASM	Assembly	SolidWorks
SLDDRW	Drawing	SolidWorks
SLI	Slide	MAGICorp Slide Service
SLK	Microsoft Excel import format	Microsoft Excel
SLK	SYLK Symbolic Link format data file	MultiPlan
SLL	Sound data file
SLL	Static Link Library	PowerBASIC
SLP	SLP command file created by SRCCOM	RT-11
SLP	Localization project file	Sisulizer
SLT	SALT Script Application Language for Telix script source	Telix
SLV	Solution for any game	many
SM	Maillist	SoftSpoken Mailer
SM	Script	ScriptMaker
SM	SMALLTALK source code file
SM	Text file	Samna Word
SM	StepMania Step File	StepMania
SMC	Super MagiCom SNES ROM image	Super MagiCom
SMCLVL	Secret Maryo Chronicles Level	Secret Maryo Chronicles
SMF	Fax	SMARTFAX
SMF	3D World Studio mesh files
SMK	Smacker Video Format (RAD Video)
SML	System Macro Library	RT-11
SMM	Ami Pro Macro File	Ami Pro
SMN	Font (ParaGraph's WorkScript format)
SMP	Sample (sound file)
SMP	Samplevision File	Samplevision
SMPL	Data	Megahedron 3D object
SMS	MSTS Sound management system file	MSTS
SMT	Text file	Smart Ware II
SN	Compressed song file	Sound Club editor
SND	Digitized sound file	Macintosh/ATARI/PC
SND	Power Chords drum sound file	Power Chord
SNDB	SQLNotes database	SQLNotes
SNG	Song (midi sound)	Midisoft Studio - Prism
SNG	Saved game file for StarCraft	StarCraft
SNO	SNOBOL4 source code file
SNP	Book-shelf for .BOO	READIBM
SNP	Microsoft Access report snapshot
SNP	Output video format from Computer Eyes equipment
SNX	Saved game file for StarCraft: Brood War	StarCraft: Brood War
SO	shared object, dynamically linked library	Unix
SOAR	Soar Production file
SOF	Altera FPGA programming file (internal RAM)	Altera Quartus
SOL	Solution e.g. game walkthroughs
SOL	Adobe Flash shared object ("Flash cookie") (Movie, film, video and multimedia file type)	Adobe Flash
SOM	Network serial numbers	Quattro Pro
SOM	Sort information	Paradox
SON	Song	SBStudio II
SOU	Temporary BATCH file	RT-11
SOU	SBStudio II Sound File	SBStudio II
SOU	Sound data (sound tool)
SP	Archive (unix)	SPLINT
SPC	Program	Microsoft Multiplan
SPC	Temporary file	WordPerfect for Win
SPC	SNES SPC-700 Sound File	SNES games
SPC	Spectroscopic data (scientific)	Thermo Scientific
SPD	Scalable font	Speedo - Harvard Graphics 3.0
SPF	Slide presentation file	EnerGraphics
SPF	data	SQR Portable Format
SPG	Glossary	Sprint
SPI	Graphics (Siemens and Philips scanner)
SPIFF	Still Picture Interchange File Format
SPIN	Spin source file	Parallax Propeller Microcontrollers
SPL	Archive	SPLINT
SPL	Customized printer driver	Sprint
SPL	Divided file segment	Slice
SPL	Personal spell dictionary	Signature
SPL	Print spooling file	Windows 3.x
SPL	Sample
SPM	Data wp{wp}.spm	WordPerfect
SPP	Printer file	Sprint
SPR	Document letter	Sprint
SPR	Generated executable screen file	FoxPro
SPR	Sprite
SPR	Story Board sprites
SPS	Exported SyncBack profile	SyncBack
SPS	Screen driver	Sprint
SPS	SPSSx source code file	VAX/VMS
SPT	Data support file (MITAC disk/system management utility pack)	MITAC disk/system management utility pack
SPT	SPITBOL source code file
SPW	Worksheet	SigmaPlot
SPX	Compiled executable screen file	FoxPro
SPX	Ogg Speex bitstream	Xiph.Org Foundation
SQD	Squish message base	Squish
SQI	Squish message base index	Squish
SQL	SQL language code	Any SQL database
SQL	Squish message base lastread pointers	Squish
SQM	Windows Live Messenger log file
SQN	Note file	SquareNote
SQZ	Archive	SQUEEZE
SQZ	FOXPRO Squeeze file	FOXPRO
SRC	Source code	Aurora Compiler
SRC	Multi-edit source	Multi-Edit
SRC	Source	DataFlex
SRF	Sun Raster File graphics file
SRP	Script	QuickLink
SRT	Subtitle format	SubRip
SS	Bitmap graphics	Splash
SS	Screen saver	DN
SSC	Celestia Solar System Catalog file	Celestia
SSD	Datafile	SAS/PC
SSF	Graphic file	SnagIt Studio File/PC
SSG	Saved game	Simsig
SSIF	Stereoscopic Interleaved file	Media playback devices / software that supports Blu-ray 3D
SSP	Datafile	SAS Transport
SSR	FLEXIT Singleshot Survey Raw Data file	FLEXIT
SST	AVHRR graphic file
SSV	Spreadsheet viewer file
ST	Instrument library	Scream Tracker
ST	SMALLTALK source code file	Little Smalltalk
ST	Stamp	NeoPaint
STA	Data file	Statistica
STA	Saved state	Reflection 4.0
STA	Stack	Spinmaker Plus
STB	Symbol table file	RT-11
STB	Stub library	Genus GX Kernel
STC	Celestia Star Catalog file	Celestia
STC	OpenOffice.org XML spreadsheet template	OpenOffice.org Calc
STD	State Transition Diagram graphic file	Prosa
STD	OpenOffice.org XML drawing template	OpenOffice.org Draw
STEAMSTART	STEAMSTART file	Steam (software)
STF	Archive	SHRINKTOFIT
STF	Setup Table File
STI	OpenOffice.org XML presentation template	OpenOffice.org Impress
STK	eBook	Starebook
STL	Stereolithography Interface Format
STL	Subtitle files EBU-standard
STM	Music format (4 channels) (Scream Tracker Module)	ST - DMP
STM	State Transition Diagram model file	Prosa
STO	Pascal stub OBJ file	Genus GX Kernel
STP	Subtitler Project	Belle Nuit Subtitler
STR	Gate3 table structure file
STR	Structure list object file	dBASE Application Generator
STR	PlayStation video file
STS	Music format (Scream Tracker Song)	ST 2.0-2.3
STS	Project status info	Microsoft C/C++
STU	Studio Project	Pinnacle Studio (video editing software)
STUFF	EVE Online compressed file archive	CCP hf.
STW	Data file	SmartTerm for Windows
STW	OpenOffice.org XML text document template	OpenOffice.org Writer
STX	Electronic book	SmarText
STX	Music format
STX	Tax form	CA-Simply Tax
STY	Ami Pro Template (Style); used by other programs for `styles`	Ami Pro
STY	Style library or sheet	many
SU?	Packed mail	FTN software
SUB	Subtitle format	SubViewer; Author David Dolinski
SUF	Sony camera configuration file (setup.suf)	XDCAM-EX camcorders
SUI	SUIT library	Simple User Interface Toolkit
SUM	Summary
SUN	Sun rasterfile graphics file	Sun Microsystems
SUO	Solution User Options	Microsoft Visual Studio
SUP	Subtitle file (Blu-ray encapsulated container)	SupRip
SUP	Supplementary dictionary	WordPerfect for Win
SV6	Saved Game File	RollerCoaster Tycoon 2
SVC	Represents the ServiceHost instance hosted by Internet Information Services	Windows Communication Foundation
SVD	Autosave file for document	Microsoft Word
SVG	Autosave file for glossary	Microsoft Word
SVG	Scalable Vector Graphics	many
SVQ	MRC-Pro sequencers music format	Roland Corporation synths such as XP or Fantom series
SVS	Autosave file for style sheet	Microsoft Word
SVW	Super Video Windows	Conversion Artist
SVX	Interchange, 8SVX/16SV	AWAVE
SVY	FLEXIT Survey data	FLEXIT
SW	Raw Signed Word (16bit) data	AWAVE
SWF	Shockwave Flash	Macromedia
SWG	SWAG Pascal Snippets file	SWAG
SWP	Document backup	Sprint
SWP	Swap file
SWT	Hump Routes File	FYM
SXC	OpenOffice.org XML spreadsheet	OpenOffice.org Calc
SXD	OpenOffice.org XML drawing	OpenOffice.org Draw
SXG	OpenOffice.org XML master document
SXI	OpenOffice.org XML presentation	OpenOffice.org Impress
SXM	OpenOffice.org XML formula	OpenOffice.org Calc
SXP	3DS Process file	3D Studio
SXW	OpenOffice.org XML text document	OpenOffice.org Writer
SY1	SmartPix symbol library	Ami Pro
SY3	Harvard Graphics format
SY3	Symbol file	Harvard Graphics 3.0
SYD	Backup of startup files created by QEMM (?) autoexec.syd
SYD	Sysedit backup file	Sysedit
SYG	Monitor and handler files created by SYSGEN	RT-11
SYM	Compiler symbolic information file
SYM	P-CAD component (symbols)	P-CAD
SYM	Precompiled headers	Borland C++
SYM	Program symbol table	Power C, Microsoft ILink incremental linker
SYM	Symbol file	Harvard Graphics 2.0, Microsoft Windows SDK
SYN	SDSC Synu image file	SDSC Image Tool
SYN	Synonym file	Microsoft Word 5
SYS	Datafile	SYGRAPH - SYSTAT - SPSS/PC
SYS	System file - device driver or hardware configuration info	DOS
SYW	Graphics file (symbol)	Harvard Graphics Win
SYW	Yamaha SY-85/SY-99 Wave File	Convert (c) Villena

T

Ext.	Description	Used by
T	Archive without compression (tape)	tar
T	TADS source
T	Tester symbol table	ReaGeniX code generator
T?H	Turbo Help file (Pascal, C, Assembler, ...)	Borland Thelp
T$M	AVG scan log files	AVG
T2B	Bookeen Cybook thumbnail	Cybook
t2flow	Taverna 2 workflow definition	Taverna workbench
T2L	True2Life file format	3D Internet content developers
T44	Temporary file for Sort or Index	dBASE IV
T64	Program	C64S emulator
TAG	Query tag name	DataFlex
TAH	Help file for Turbo Assembler	Borland C++
TAL	Adobe Type Align	Adobe
TAL	Text illustration	TypeAlign
TAP	Tape file	ZX Spectrum emulator by g.a.lunter
TAR	Archive	TAR
TAZ	Archive	WinZipNT - TAR - COMPRESS
TB	Tab file (Virtual Desktop Tab)	Tabbery
TB1	Font file	Borland Turbo C
TB2	Font file	Borland Turbo C
TBF	Fax	Imavox TurboFax
TBK	FOXPRO template backup file	FOXPRO
TBK	Memo backup	dBASE IV - FoxPro
TBK	Toolbook	Asymetrix ToolBook
TBL	Short for Table	used by many programs
TBL	Aldus TableEditor file	TableEditor
TBL	Gate3 table file
TBL	Graphics file (native format)	PageMaker TableEditor
TBL	Table of values	OS/2
TBR	Norton Desktop custom toolbar	NDW
TBS	Text elements ?? (Textbausteine)	Microsoft Word
TBX	Table	Project Scheduler 4
TBZ	Archive	WinZipNT - TAR - Bzip2
TC	Configuration	Turbo C - Borland C++
TCH	Help file	Turbo C - Borland C++
TCL	Tool Command Language source code	Swat
TCT	Drawing Template	TurboCAD for Windows
TCW	Native Drawing File	TurboCAD for Windows
TD	Config from Turbo Debugger	Turbo Debugger
TD0	Compressed diskette in a file	Teledisk
TD2	Configuration file	Turbo Debugger for Win32
TDB	Database	TACT
TDDD	Imagine Object File Format
TDF	Speedo font file
TDF	Typeface definition file	Speedo
TDH	Help file for Turbo Debugger	Borland C++
TDK	Keystroke recording file	Turbo Debugger
TDR	Contens of Arvid tape
TDS	Symbol table	Turbo Debugger
TDT	Thumbnail data	AVCHD
TDW	Configuration file	Turbo Debugger for Windows
TEC	Data	TECPLOT output
TEC	TECO macro file ("compiled" form)	TECO
TEF	Fax	Relisys TEFAX
TEL	Host file	Telnet
TEM	Input template	IconAuthor
TEM	Turbo Editor Macro Language script	Borland C++
TERM	Terminal File
TES	TECO macro file (source form)	TECO
TET	Tetris results	DN
TEX	Datasheet	Idealist
TEX	TeX text file	Scientific Word - TeX
TEX	Image	Slimtex
TEXT	Text file
TF	Configuration	Turbo Profiler
TFA	Area file	Turbo Profiler
TFC	Catalogue file	Tobi's Floppy Cataloguer
TFF	self executing TansForm dialogue	TansForm
TFH	Help file for Turbo Profiler	Borland C++
TFM	Tagged font metric file	Intellifont
TFM	TeX Font Metric file	TeX
TFS	Statistical information	Turbo Profiler
TG1	Project file	On Target
TGA	Targa True Color bitmapped format	Paint.NET
TGZ	Archive	WinZipNT - TAR - GNUzip
TH?	Packed mail	FTN software
THE	Windows'95 Desktop Theme	Microsoft Plus
THM	Thumbnail or Theme File	Picture Publisher, PhotoMagic, Canon Digital Cameras, and Sony Digital Cameras will create these Thumbnail files. Also using the same file extension is Sony Ericsson Theme File, for a cell phone.
THP	Nintendo proprietary video format	Various Nintendo games
THS	Thesaurus dictionary	WordPerfect for Win
TIB	Acronis True Image Backup	Acronis True Image
TIC	FTN special file with assotiated file description	ALLFIX
TIF	see TIFF
TIFF	TIFF (tagged image format file) bitmapped file	Alchemy - PhotoStyler -PageMaker - CorelDRAW
TIL	Fuzzy logic knowledge base	Togai InfraLogic Fuzzy-C Compiler
TIP	Digital Signage Presentation	Tru-Designer, Tru-Player, Tru-Scheduler part of Tru-i Suite
TIS	Tile set	MahJongg 3.0
TJL	Backup file	VAXTPU editor
TLB	Interoperability Type Library	Win95
TLB	Reference table	Bubble Chamber
TLB	Text library	VAX
TLB	Type library	Visual C++
TLC	Compiled Tool Command Language source code	Swat
TLD	Disk Image	Teledisk
TLH	Typelib Generated C/C++ Header	Visual C++
TLP	Project	TimeLine
TLX	Website builder	Trellix
TM2	Typical Meteorological Year data (new)	Typical Meteorological Year
TMF	Tagged Font Metric file	WordPerfect for Win
TMF	TiVo movie	TiVo
TMO	ZTG global optimizer default output file	Zortech C++
TMO	HandsHigh ThoughtManager Outline	ThoughtManager Desktop
TMP	Temporary file	ALL PROGRAMS
TMS	TeleMate compiled script	TeleMate
TMY	Typical Meteorological Year data (old)	Typical Meteorological Year
TMY2	Typical Meteorological Year data (new)	Typical Meteorological Year
TOC	Table Of Contents text file (ASCII)
TOK	Borland C++ 4.x reserved word list	BCW.EXE
TOPC	TopicCrunch SEO Project file holding keywords, domain and search engine settings (ASCII)
TORRENT	TORRENT File	BitTorrent clients (various)
TOS	Character file	The Only Sheet
TOS	Self-extracting file archive (Atari ST)
TP	Session-state file	Turbo Profiler
TP	Turbo Pascal cfg file	Turbo Pascal
TP	TinkerPlots Document	TinkerPlots and Fathom Dynamic Data Software. Documents contain data tables, graphs, text, pictures, etc.
TP3	Template	Harvard Graphics 3.0
TPB	Downloadable PCL Soft font file backup	HiJaak
TPC	File produced when an inter-Topicscape topic link file is exported to Windows	3D Topicscape
TPF	Downloadable PCL Soft font file	HiJaak
TPF	Print data in EMF format	ThinPrint
TPH	Help file	Turbo Pascal
TPL	Resident units library	Turbo Pascal
TPL	Template file	GoldEd -ITrack
TPL	Template	Harvard Graphics 2.0
TPOLY	Data	TPOLY 3D object
TPP	Protected Mode Units	Borland Pascal 7.0
TPT	Digital Signage Presentation Template	Tru-Designer, Tru-Scheduler part of Tru-i Suite
TPU	Borland Pascal DOS Mode Library	Borland Pascal
TPU	Command file (VAXTPU editor)	VAXTPU editor
TPW	Borland Pascal Windows Library	Borland Pascal
TPW	Session-state file	Turbo Profiler for Windows
TPZ	Archive	TAR - GNUzip
TR	Man page input suitable for troff -man	cawf2.zip
TR	Session-state settings	Turbo Debugger for DOS
TR2	Session-state settings	Turbo Debugger for Win32
TRC	Debug support file	Power CTrace
TRASH	File found during a file scan as bugged	Windows
TRE	Directory tree file	PC-Tools
TRD	Datafile	TrID file identifier filetypes definitions package
TRIA	Data	Greg Hood's ASCII Triangle
TRIB	Data	Greg Hood's Binary Triangle
TRIF	Tiled Raster Interchange Format
TRK	Track (i.e. video sequence), used by many games
TRM	Terminal settings	Windows 3.x
TRN	Translation support file	Quattro - Clarion
TRS	Executable file	Micrografx or password file
TRS	WiSo Mein Geld 2007
TRS	IBM Mainframe log file	TRSMAIN
TRU	True Basic source file
TRW	Session-state settings	Turbo Debugger for Windows
TRY	Typical Meteorological Year data (variant)	TRNSYS
TS	MPEG Transport Stream	Various media players / software
TS	Qt Linguist TS File	Trolltech Qt Linguist
TSE	Data	Light Map Maker ASCII Scene
TSK	Microsoft Multimedia Task Application	Win95
TSL	Exported Schedule	Tru-Scheduler part of Tru-i Suite
TSM	Turbo Assembler Manual	TASM for OS/2
TST	Printer test file	WordPerfect for Win
TSV	Tab Separated Values
TTF	TrueType Font file
TU?	Packed mail	FTN software
TUD	The Ultimate Draw file	The Ultimate Draw
TUT	Tutorial
TV	Table view settings	Paradox
TVF	Table view settings	dBASE
TVn	Overflow file above insert point in Doc n	WordPerfect for Win
TXC	Test Configuration Format
TXF	Tax eXchange Format
TXI	Support file	TeX
TXT	Common name for ASCII text file
TXT	Tab-Delimited Text File	Microsoft Excel
TXW	Yamaha TX-16W Wave File	Convert (c) Villena
TY	TiVo movie	TiVo
TYM	Time Stamp (PageMaker 4)	PageMaker 4
TZ	Archive	TAR - COMPRESS
TZB	Archive	TAR - COMPRESS - BTOA
TZL	Tanzzle pattern file	Tanzzle
TZX	Tanzzle image file	Tanzzle

U

Ext.	Description	Used by
U3D	Model file format	Ultimate 3D
U3D	Universal 3D	Adobe Acrobat
U8	Sample
UB	Raw Unsigned Byte (8bit) data	AWAVE
UC2	Archive	UC II
UCN	New archive	UC II
UCS	Unknownsoft Service Pack (mainly for Shadow OS 2009)	Unknownsoft Computer Systems
UDF	Filter	Aldus Photostyler
UDO	Data	Moray User Defined Object
UDIWWW	bookmark data	UdiWWW
UDW	Raw Unsigned DWord data	AWAVE
UE2	Encrypted archive	UC II
UFI	data	UFO CaptureV2 settings -
UFO	graphic file	Ulead Photo Impact
UHA	UHarc archive
UHS	Universal Hint System (binary file)
UI	Espire source code file	Geoworks UI Compiler Geos
UI	Qt Designer's UI File	Trolltech Qt Designer
UI	User interface	Sprint
UIF	Long prompts for windows	WordPerfect for Win
UIH	Espire header file	Geoworks UI Compiler Geos
UL	ULAW audio file
ULD	Information about uploaded files	Procomm Plus - Datastorm Technologies, Inc.
ULF	data	MRF Mapping Tool Kit Universal List Format
ULT	Music	UltraTracker
UMB	Backup file	MemMaker
UNF	Universal NES Image Interchange File Format
UNI	Datafile	Forecast Pro
UNI	Music format	UNIMOD - MIKMOD
UNIF	Universal NES Image Interchange File Format
UNV	Text file containing finite elements nodal coordinates and more. See notes	Originally used by SDRC for its I-deas software, a lot of simulation software use it today.
UNX	Text file containing UNIX specific info
UOML	UniqueObject Markup Language (UOML) is a XML-based markup language
UOP	Uniform Office Format presentation
UOS	Uniform Office Format spreadsheet
UOT	Uniform Office Format text
UPD	Update data	dBASE
UPO	Compiled update data	dBASE
URL	Internet Shortcut (URL)	Windows Explorer
URT	Utah Raster Toolkit
USE	Log file
USP	Printer font with USASCII extended character set	Adobe PageMaker
USR	User database file	Procomm Plus - Turbo C++ tour
UST	UTAU vocal track	UTAU
UT!	datafile	uTorrent
UTZ	Mobile Phone Theme	Sony Ericsson
UU	Encoded file (ASCII)	UUENCODE/UUDECODE - Uuencoding
UUE	Encoded file (ASCII)	UUENCODE/UUDECODE - Uuencoding
UW	Raw Unsigned Word 16bit data	AWAVE
UWF	UltraTracker WaveSample	UltraTracker

V

Ext.	Description	Used by
V	Consistency check support file	ReaGeniX code generator
V	Main input file for an image	Vivid 2.0
V	Coq source file
V	Verilog source file
V1, V2, ...	Split parts of a whole file	JJSplit
V8	Covox 8bit file	AWAVE
V10	Data	Gouraud Shaded Vectors
V2D	Voucher design file	Voucher management included in JFire (e.g. when printing a voucher)
VAI	multimedia	PhotoDub document
VAL	Validity checks and referential integrity	Paradox for Windows
VAL	Values list object file	dBASE Application Generator
VALA	Sourcecode	Vala
VAN	Animation	VistaPro
VAP	Value Added Process	NetWare 2.xx
VAP	Dialogic indexed adpcm voice file	VBASE/40
VAR	Variable file	IconAuthor
VB	Visual Basic .Net source file	Visual Basic .NET
VBPROJ	Visual Basic .Net project file.	Visual Basic .Net Express and Visual Studio 2003-2010 Project File for projects containing Visual Basic code.
VBR	Visual Basic Custom Control file	Visual Basic
VBS	VBScript script file	VBScript
VBX	Visual Basic eXtension	Visual Basic
VBZ	Visual Basic Setup Wizard Template	Setup Wizard
VC6	Graphite - 2D and 3D drafting	Ashlar-Vellum
VC	Include file with color definitions	Vivid 2.0
VC	Spreadsheet	VisiCalc
VCA	Visual Clip Art
VCD	VideoCD
VCD	VirtualDrive CD Image File
VCD	Value Change Dump (Verilog) temporal database file
VCD	VisualCADD Drawing File
VCR	VCR drivers for Arvid
VCW	Visual workbench information	Microsoft Visual C++
VCX	Spreatsheet	VisiCalc Advanced
VDA	Bitmap graphics
VDO	Story Board video image	Story Board
VDR	Drawing	ComputerEasy Draw
VEG	Vegas Project	Sony Vegas
VEW	GroupWise for Windows	Win
VEW	View file	Clipper 5 - Lotus Approach
VFA	FontLab Database file	FontLab
VFD	Virtual Floppy Disk	Windows Virtual PC (among others)
VFM	Ventura Font Metrics file
VFM	Voting Form	Voter
VFN	Voting Form for Customers	Voter
VGA	VGA display driver
VGA	VGA display font
VGD	VGA display driver	Generic CADD
VGM	Video Game Music audio format.
VGR	Graphics file	Ventura Publisher
VHD	Virtual Hard Disk	Windows Virtual PC (among others)
VI	LabVIEW Virtual Instrument	LabVIEW
VI	Graphics file	Jovian Logic VI
VI	Watcom editor script	VI.EXE
VIA	VIA Document Project	VIA Text Editor
VIC	see VICAR
VICAR	Graphics (Video Image Communication and Retrieval)
VID	Bitmap graphics (YUV12C M-Motion Frame Buffer)
VID	Graphics format	Word&Deed
VID	MS-DOS Shell Monitor file	MS-DOS 5
VID	Screen device driver	Word
VIF	see VIFF
VIFF	Khoros Visualization Image File Format	SDSC Image Tool
VIK	Graphics format (VIKING)
VIM	Vim script file	Vim text editor
VINF	data	ReMPEG log file - frames info
VIR	Virus or infected file
VIS	VIS graphics file
VLM	Vellum, Vellum 2D, Vellum Draft, Vellum 3D, DrawingBoard	Ashlar-Vellum
VLM	Virtual Loadable Module	Netware
VM	Virtual Memory file	Geoworks
VMC	Virtual memory configuration	DOS/4GW PM 32X DOS Extender
VMDK	Virtual Disk file	VMware
VMF	Font characteristics	Ventura Publisher
VMG	Nokia message file format	Text Message Editor (Nokia PC Suite)
VMS	Text file containing VMS specific info
VO	Include file with object definition	Vivid 2.0
VOB	Video Object	DVD-R, DVD-RW
VOC	Sound format (Creative Lab's Sound File)	PlayVoc
VOF	Object folder	VZ Programmer
VOP	Visual Orangator Project
VOP	Visual OTTHYMO Project
VOX	Dialogic adpcm file	AWAVE, CoolEdit
VP	3DS Video posting	3D Studio
VPF	Vector Product Format
VPG	Graphics file	VPGraphics
VPH	Virtual Pascal Help	VP/OS2
VPI	Virtual Pascal Unit	VP/OS2
VQA	Vector Quantized Animation	The Legend of Kyrandia
VRM	Overlay file	QuattroPro
VRM	Visual rexx source	WATCOM VREXX
VRML	Virtual Reality Modeling Language	NetScape
VRP	Project	WATCOM VX?Rexx
VRS	Video Resource e.g. video device driver	WordPerfect
VS	Vellum Solids	Ashlar-Vellum
VS	Include file with surface definition	Vivid 2.0
VSD	Diagram	Shapeware Visio
VSD	Visio drawing	Visio
VSM	Visual Simulation Model	VisSim
VSP	Sprite	SPX
VSQ	Vocal track data	Vocaloid2
VSS	SmartShapes file	Shapeware Visio
VSS	Visio Template	Visio
VST	Truevision Vista graphics file
VST	Visio Template	Visio
VSTO	Microsoft Office add-in file	Microsoft Visual Studio
VUE	Animation	3D Studio
VUE	View	dBASE IV - FoxPro
VW	Text file	VolksWriter
VWR	File viewer file	PC Tools
VWX	CAD File	VectorWorks 2008
VXD	Windows 3.x virtual device driver	Windows 3.x
VZT	Temporal database file	GTKWave data file

W

Ext.	Description	Used by
W	Word chart file	APPLAUSE
W01	Yamaha SY-series wave files	AWAVE
W01	Yamaha TX16W wave file	AWAVE
W30	Printer font	AST TurboLaser - Ventura Publisher
W31	Startup file	Windows 3.1
W3A	Warcraft III Abilities Export File	Contained in a Warcraft III map
W3B	Warcraft III Destructables Export File	Contained in a Warcraft III map
W3D	Warcraft III Doodads Export File	Contained in a Warcraft III map
W3D	Westwood 3D object format.	3D models used in Renegade and Generals.
W3D	Shockwave 3D object format.
W3G	Warcraft III Replay File	File for Warcraft III
W3H	Warcraft III Buffs Export File	Contained in a Warcraft III map
W3M	Warcraft III Map	File for Warcraft III: Reign of Chaos
W3N	Warcraft III Campaign	File for Warcraft III: The Frozen Throne
W3O	Warcraft III Object Data Export File	Contained in a Warcraft III map
W3P	Warcraft III Save	Save File for Warcraft III
W3Q	Warcraft III Upgrades Export File	Contained in a Warcraft III map
W3T	Warcraft III Item Export File	Contained in a Warcraft III map
W3U	Warcraft III Unit Export File	Contained in a Warcraft III map
W3V	Warcraft III Save	Save File for Warcraft III
W3X	Warcraft III Expansion Map	File for Warcraft III: The Frozen Throne
W3Z	Warcraft III Save	Save File for Warcraft III
W40	Something for Windows95 (e.g. config.w40)	Win95
W44	Temporary file for Sort or Index	dBASE
W95	Something for Windows95	Win95
WAD	Where's All the Data?	Doom - Doom2
WAD	Nintendo proprietary format for Wii channels, menus, etc.	Nintendo Wii
WAG	Yard Contents File	FYM
WAI	Warcraft III AI Data File	Warcraft III AI Data File
WAR	Java Web Archive	A Java file format used to package and deploy web applications.
WAS	ProComm Script File (source code)	ProComm
WAV	Sound format (Microsoft Windows RIFF WAVE)	Media Player
WAX	TVTonic WAX video packaging	Wavexpress TVTonic
WAX	ProComm compiled script	ProComm
WB1	Notebook	Quattro Pro
WB2	Spreadsheet	Quattro Pro
WBF	Microsoft Windows Batch File	Catch
WBK	Document/workbook or Microsoft Word backup file	WordPerfect for Win or Microsoft Word
WBT	Norton Desktop	Norton Desktop
WBT	Wilsonware Batch file	Winbatch
WCD	Condes Event Data file	Condes
WCD	Macro token list	WordPerfect for Win
WCH	WordPerfect Macro Facility	WP
WCM	Data transmission file	Microsoft Works
WCM	Macro	WordPerfect for Win
WCP	Product information description	WordPerfect for Win
WD	InfoSelect Data file
WDB	Database	Microsoft Works
WDM	Admin tool connection definition	War FTP
WE?	Packed mail	FTN software
WEB	WEB source code file	Web Easy Professional
WebOOGL	Web Object Oriented Graphics Library
WFB	Turtle Beach WaveFront Bank	AWAVE
WFD	Turtle Beach WaveFront Drum	AWAVE
WFM	Form object	dBASE Form Designer
WFN	Font	CorelDRAW
WFP	Turtle Beach WaveFront Prog.	AWAVE
WFT	Web Family Tree	GRAMPS
WFX	Data file	Winfax
WG1	Worksheet	Lotus 1-2-3/G
WG2	Worksheet	Lotus 1-2-3 for OS/2
WID	Width table	Ventura Publisher
WIM	Windows Imaging Format	ImageX
WIN	Window file	FoxPro - dBASE
WIREFRAME	Data	EMSE mesh
WIX	Windows Installer XML	WiX
WIZ	Page wizard	Microsoft Publisher
WK1	Spreadsheet	Lotus 1-2-3 version 2.x - Lotus Symphony 1.1+
WK3	Spreadsheet	Lotus 1-2-3 version 3.x
WK4	Spreadsheet	Lotus 1-2-3 version 3.4
WKB	Document	WordPerfect for Win
WKE	Spreadsheet	Lotus 1-2-3 educational version
WKF	VISI Working file	Vero Software
WKI	Spreadsheet format	Lotus 123 2x
WKQ	Spreadsheet	Quattro
WKS	Spreadsheet	Lotus 1-2-3 version 1A - Lotus Symphony 1.0, Microsoft Works
WKS	Workspace	Xlisp
WKZ	Spreadsheet format	Dos Navigator
WLK	Graphics	Virtus Walkthrough
WLK	Walk Through for any game	many
WMA	Windows Media Audio audio file
WMC	Backup of startup files by Windows MathCad autoexec.wmc	MathCad
WMC	Macro file	WordPerfect for Win
WMC	Text file	WordMARC
WMDB	Windows Media Player database	Windows Media Player
WMF	Windows MetaFile vector graphics
WMO	WoW Map Object	Blizzard Entertainment games (World of Warcraft/Warcraft series)
WMP	Graphics (Windows Magic Icon Palette)
WMV	Windows Media Video video file
WN	Text	NeXT WriteNow
WNF	Corel Draw Font File	CorelDraw
WOA	Swap file	Windows 3.x
WOC	Organization	Windows OrgChart
WOW	Music (8 channels)	Grave Mod Player
WP	Word Perfect Format	WP
WP5	Document	WordPerfect 5.x
WPD	Document	WordPerfect 6.0 - PFS:WindowWorks
WPD	Windows printer driver (uninstallable)	Windows
WPF	Fax	WorldPort
WPF	Form	WordPerfect
WPG	WordPerfect Graphics vector graphics	DrawPerfect
WPJ	Watcom C/C++ IDE project	IDE.EXE
WPK	Macros	WordPerfect for Win
WPL	MediaRack Wave Playlist	MediaRack
WPL	Windows Media Playlist, for Windows Media Player
WPM	Macros	WordPerfect
WPS	Text document	Microsoft Works
WQ!	Compressed spreadsheet	Quattro Pro
WQ1	Spreadsheet	Quattro Pro
WR1	Spreatsheet	Lotus Symphony 1.1 - 1.2 - 2
WRD	Template	Charisma
WRI	Write editor format	Write - WinWord
WRK	Spreadsheet	Lotus Symphony 1.0
WRL	VRML file
WRP	Archive	Amiga WARP
WRS	Windows Resource e.g. might indicate error if word cannot open	WordPerfect for Win
WS	APL Worksheet
WS	Text file	WordStar 5.0-6.0
WS2	Text file	WordStar 2000
WSD	Document	WordStar
WSP	Workspace	Fortran PowerStation
WSQ	Wavelet-packet Scalar Quantization Format
WSRC	X-wais source
WST	Text file	WordStar
WTR	Working Timetable rules file	Simsig
WTT	Working Timetable timings file	Simsig
WTF	World of Warcraft Data File	World of Warcraft
WTF	WinTaper Data
WWB	Button bar for document window	WordPerfect for Win
WWF	WWF Document Format
WWK	Keyboard layout	WordPerfect for Win
WXH	Program/Script File	WaxHtml Web Programming Language
WXP	Document	EXP for Windows

X

Ext.	Description	Used by
X	Archive	X1.EXE
X ;	AVS X image file	SDSC Image Tool
X	DirectX 3D object
X	LEX source code file
X	XBasic Source code file	Xbasic
X3D	x3d and xdart Formats
XA	XA audio file	used in SimCity 3000 by Maxis, also by Sony PlayStation
XAR	Xara graphics file	Files created by Xara Photo & Graphic Designer (formerly Xara Xtreme and Xara Studio). Early versions used the extension 'ART'.
XBE	Xbox Executable	Xbox
XBM	X11 Bitmap graphics file
XCF	Gimp image file	The Gimp
XCK	Extended crack file (usually text)
XCL	Xtree for Windows Script file	Xtree for Win
XDF	OS/2 extended disk format image	XDFCOPY.EXE
XDM	Directory Manipulator for 32-bit Protected Mode	Xenotech Research Labs
XE	Xenon - for Associative 3D Modeling	Ashlar-Vellum
XEX	Xbox 360 Executable File
XFN	Printer font	Xerox 4045 - Ventura Publisher
XFR	Ventura Publisher Bitmap Editor Font file
XFT	24 pin printer font	ChiWriter
XI	Fast Tracker 2 instrument file	AWAVE
XI	Fastracker 2.0 Instrument File	Fastracker 2.0
XIF	Xerox Image Format	Pagis Pro 2.0 and 3.0
XLA	Add-in macro sheet	Microsoft Excel
XLA	XLib Archive	xlibpas2.zip
XLB	Microsoft Excel Toolbar	Microsoft Excel
XLC	Microsoft Excel Chart	Microsoft Excel
XLD	Microsoft Excel Dialog	Microsoft Excel
XLF	Extensible LADAR Format	LadarSIM
XLK	Microsoft Excel Archive	Microsoft Excel
XLL	Microsoft Excel Dynamic Link Library	Microsoft Excel
XLM	Microsoft Excel Macro File	Microsoft Excel
XLS	Microsoft Excel Spreadsheet	Microsoft Excel
XLSB	Microsoft Excel 2007 Binary Workbook (BIFF12)(Spreadsheets)	Microsoft Excel 2007 (see Microsoft Office 2007 file extensions)
XLSM	Microsoft Excel 2007 Macro-Enabled Workbook (Spreadsheets)	Microsoft Excel 2007 (see Microsoft Office 2007 file extensions)
XLSX	Office Open XML Workbook (Spreadsheets)	Microsoft Excel 2007 (see Microsoft Office 2007 file extensions)
XLT	Microsoft Excel Template	Microsoft Excel
XLT	Translation table	Lotus 1-2-3 - Symphony - Procomm Plus
XLV	Microsoft Excel Module	Microsoft Excel
XLW	Microsoft Excel Workbook	Microsoft Excel
XM	Fast Tracker 2 extended module	AWAVE, Mod4Win, FastTracker, ImpulseTracker
XM	Music format	FastTracker - Cubic Player
XMC	Assisted contact lists file format, based on xml and used in kindergartens and schools	Classmates iPhone app
XMOD	Monarch Model	Monarch Professional
XMI	Compressed eXtended MIdi music
XML	eXtensible Markup Language file
XMF	eXtensible Music Format
XMPZ	XML Miradi Project Zipfile	Miradi
XMV	video	Xbox
XNF	Standard Network File form
Xnn	Secondary indexes	Borland Paradox
XOF	RenderMorphics
XP	eXtended Pattern	FastTracker 2.0
XPM	X11 Pixel Map graphics file
XPO	Microsoft Dynamics AX Export file
XPS	Open XML Paper Specification / OpenXPS	open standard document format initially created by Microsoft and similar in concept to Adobe PDF files
XQT	Executable file	Waffle
XQT	Macro sheet	SuperCalc
XRF	Cross-reference file
XSF	data	Microsoft InfoPath file
XSPF	XML Sharable Playlist Format
XTB	External translation table	LocoScript
XTP	XTreeGold overlay	XTreeGold
XVF	Xyngo Video File	Xyngo Video Board
XWD	X Window System window dump image graphics file	SDSC Image Tool
XWK	Keyboard mapping	Crosstalk
XWP	Session	Crosstalk
XWP	Text file	Xerox Writer
XX	Encoded file (ASCII)	XXENCODE
XXE	Encoded file (ASCII)	XXENCODE
XY	Text file	XY Write
XY3	Text file	XYWrite III
XYW	Text file	XyWrite III
XYZ	Molecular coordinates	XMol, RasMol

Y

Ext.	Description	Used by
Y	Archive (Amiga)	Yabba
Y	YACC grammar file	Yacc/Bison
YAL	Data custom/nature.yal	Arts & Letters
YC	Archive	YACC (YAC.EXE)
Ynn	Secondary index	Borland Paradox
YMP	Yast Meta Package	YAST2 (SUSE Linux Package Manager)
YST	Data	YASRT Raytracer scene
YRD	Yard Tracks File	FYM
YUV	Graphics format (YUV)
YY	Bison grammar file	Bison
YZ	Archive	YAC

Z

Ext.	Description	Used by
Z	Archive	WinZipNT - COMPRESS - PACK
Z01-Z99	Split WinRAR Archive
Z2S	Zoo Tycoon 2 saved game	Any game in the Zoo Tycoon 2 series.
Z3	Infocom game module
Z3D	Zmodeler-file	Zmodeler 1 & 2
Z64	Nintendo 64 ROM	Project64 Nintendo 64 emulator
Z80	Snapshot	ZX Spectrum emulator by g.a.lunter
ZAD	ZFax digitized voice file	ZFax
ZDG	Compressed ZiffNet text document	Zview
ZED	BitTorrent Link	Podmailing
ZER	Data file
ZIP	Archive	PKZip - WinZip - Mac OS X
ZOO	Zoo Tycoon saved game	Any game in the Zoo Tycoon (first) series.
ZZT	ZZT World	Any world created using the ZZT editor.

External links

• The File Extensions Resource
• File information site
• List of File Types for Web Searches
• List of File Types