URI scheme

In the field of computer networking, a URI scheme is the top level of the Uniform Resource Identifier (URI) naming structure. All URIs and absolute URI references are formed with a scheme name, followed by a colon character (":"), and the remainder of the URI called (in the outdated RFCs 1738 and 2396, but not the current STD 66/RFC 3986) the scheme-specific part. The syntax and semantics of the scheme-specific part are left largely to the specifications governing individual schemes, subject to certain constraints such as reserved characters and how to "escape" them.

URI schemes are frequently erroneously referred to as "protocols", or specifically as URI protocols or URL protocols, since most were originally designed to be used with a particular protocol, and often have the same name. The http scheme, for instance, is generally used for interacting with Web resources using HyperText Transfer Protocol. Today, URIs with that scheme are also used for other purposes, such as RDF resource identifiers and XML namespaces, that are not related to the protocol. Furthermore, some URI schemes are not associated with any specific protocol (e.g. "file") and many others do not use the name of a protocol as their prefix (e.g. "news").

URI schemes should be registered with IANA, although non-registered schemes are used in practice. RFC 4395 describes the procedures for registering new URI schemes.

Generic syntax

Internet standard STD 66 (also RFC 3986) defines the generic syntax to be used in all URI schemes. Every URI is defined as consisting of four parts, as follows:

<scheme name> : <hierarchical part> [ ? <query> ] [ # <fragment> ]

The scheme name consist of a sequence of characters beginning with a letter and followed by any combination of letters, digits, plus ("+"), period ("."), or hyphen ("-"). Although schemes are case-insensitive, the canonical form is lowercase and documents that specify schemes must do so with lowercase letters. It is followed by a colon (":").

The hierarchical part of the URI is intended to hold identification information hierarchical in nature. Usually this part begins with a double forward slash ("//"), followed by an authority part and an optional path.

• The authority part holds an optional user information part terminated with "@" (e.g. username:password@), a hostname (i.e. domain name or IP address), and an optional port number preceded by a colon ":".

• The path part is a sequence of segments (conceptually similar to directories, though not necessarily representing them) separated by a forward slash ("/"). Each segment can contain parameters separated from it using a semicolon (";"), though this is rarely used in practice.

The query is an optional part separated with a question mark, which contains additional identification information which is not hierarchical in nature. The query string syntax is not generically defined, but is commonly organized as a sequence of <key>=<value> pairs separated by a semicolon or separated by an ampersand, for example:

Semicolon: key1=value1;key2=value2;key3=value3
Ampersand: key1=value1&key2=value2&key3=value3

The fragment is an optional part separated from the front parts by a hash ("#"). It holds additional identifying information that provides direction to a secondary resource, e.g. a section heading in an article identified by the remainder of the URI. When the primary resource is an HTML document, the fragment is often an id attribute of a specific element and web browsers will make sure this element is visible.

Examples

The following are two example URIs and their component parts (taken loosely from RFC 3986 — STD 66):

  foo://username:password@example.com:8042/over/there/index.dtb?type=animal&name=narwhal#nose
  \_/   \_______________/ \_________/ \__/            \___/ \_/ \______________________/ \__/
   |           |               |       |                |    |            |                |
   |       userinfo         hostname  port              |    |          query          fragment
   |    \________________________________/\_____________|____|/
scheme                  |                          |    |    |
   |                authority                    path   |    |
   |                                                    |    |
   |            path                       interpretable as filename
   |   ___________|____________                              |
  / \ /                        \                             |
  urn:example:animal:ferret:nose               interpretable as extension

Official IANA-registered schemes

The official URI schemes registered with the IANA are as follows (note that "IETF Draft" in no way is a finalized specification and must not be treated so; refer to Section 2.2 of RFC 2026 for more details):

Scheme	Purpose	Defined by	General format	Notes
aaa	Diameter Protocol	RFC 3588	aaa://<host>[:<port>][;transport=<transport>][;protocol=<protocol>] example: aaa://host.example.com:1813;transport=udp;protocol=radius
aaas	Secure equivalent of aaa	RFC 3588	aaas://<host>[:<port>][;transport=<transport>][;protocol=<protocol>]
acap	Application Configuration Access Protocol	RFC 2244	acap://[<user>[;AUTH=<type>]@]<host>[:<port>]/<entry>	URL scheme used within the ACAP protocol for the "subdataset" attribute, referrals and inheritance
cap	Calendar access protocol	RFC 4324	generic syntax	URL scheme used to designate both calendar stores and calendars accessible using the CAP protocol
cid	Referencing individual parts of an SMTP/MIME message	RFC 2111 RFC 2392	cid:<content-id>	e.g. referencing an attached image within a formatted e-mail. (See also mid:)
crid	TV-Anytime Content Reference Identifier	RFC 4078	crid://<host>/<data>	Allow references to scheduled publications of broadcast media content.
data	Inclusion of small data items inline	RFC 2397	data:<mediatype>[;base64],<data>
dav	HTTP Extensions for Distributed Authoring (WebDAV)	RFC 2518 RFC 4918	dav:	Used for internal identifiers only; WebDAV itself addresses resources using the http: and https: schemes. [1]
dict	Dictionary service protocol	RFC 2229	dict://<user>;<auth>@<host>:<port>/d:<word>:<database>:<n> dict://<user>;<auth>@<host>:<port>/m:<word>:<database>:<strat>:<n>	refer to definitions or word lists available using the DICT protocol
dns	Domain Name System	RFC 4501	dns:[//<host>[:<port>]/]<dnsname>[?<dnsquery>] examples: dns:example?TYPE=A;CLASS=IN dns://192.168.1.1/ftp.example.org?type=A	designates a DNS resource record set, referenced by domain name, class, type, and, optionally, the authority
fax	Used for telefacsimile numbers	RFC 2806	fax:<phonenumber>	Seems to be deprecated in RFC 3966 in favour of tel:
file	Addressing files on local or network file systems	RFC 1738 RFC 3986	file://[host]/path or (RFC 3986) file:[//host]/path	Since this usually used for local files the host from RFC 1738 is often empty leading to a starting triple /. RFC 3986 allows an absolute path with no host part.
ftp	FTP resources	RFC 1738 IETF Draft Old IETF Draft	generic syntax
geo	A Uniform Resource Identifier for Geographic Locations	RFC 5870	geo:<lat>,<lon>[,<alt>][;u=<uncertainty>] (for WGS-84)	Other coordinate reference systems (including those for non-terrestrial globes, such as The Moon and Mars) will be supported, once registered.
go	Common Name Resolution Protocol	RFC 3368	go://[<host>]?[<common-name>]*[;<attribute>=[<type>,]<value>] or go:<common-name>*[;<attribute>=[<type>,]<value>]
gopher	Used with Gopher protocol	RFC 4266	gopher://<host>:<port>/<item type>/<path>
h323	Used with H.323 multimedia communications	RFC 3508	h323:[<user>@]<host>[:<port>][;<parameters>]
http	HTTP resources	RFC 1738 RFC 2616 (makes RFC 2068 obsolete)	generic syntax
https	HTTP connections secured using SSL/TLS	RFC 2817	generic syntax
iax	Inter-Asterisk eXchange protocol version 2	RFC 5456	iax:[<username>@]<host>[:<port>][/<number>[?<context>]] examples: iax:[2001:db8::1]:4569/alice?friends iax:johnQ@example.com/12022561414
icap	Internet Content Adaptation Protocol	RFC 3507
im	Instant messaging protocol	RFC 3860	im:<username>@<host>	Works as xmpp: URI for single user chat sessions.
imap	Accessing e-mail resources through IMAP	RFC 2192 RFC 5092	imap://[<user>[;AUTH=<type>]@]<host>[:<port>]/<command>
info	Information Assets with Identifiers in Public Namespaces	RFC 4452
ipp	Internet Printing Protocol	RFC 3510
iris iris.beep iris.xpc iris.xpcs iris.lws	Internet Registry Information Service	RFC 3981 RFC 3983 RFC 4992 RFC 4992 RFC 4993
ldap	LDAP directory request	RFC 2255 RFC 4516	ldap://[<host>[:<port>]][/<dn> [?[<attributes>][?[<scope>][?[<filter>][?<extensions>]]]]] example: ldap://ldap1.example.net:6666/o=University%20of%20Michigan, c=US??sub?(cn=Babs%20Jensen)
lsid	Life Science Identifier	dtc/04-10-08	URN:LSID:<Authority>:<Namespace>:<ObjectID>[:<Version>] example: urn:lsid:ubio.org:namebank:11815
mailto	SMTP e-mail addresses and default content	RFC 1738 RFC 2368 IETF Draft	mailto:<address>[?<header1>=<value1>[&<header2>=<value2>]] example: mailto:jsmith@example.com?subject=A%20Test&body=My%20idea%20is%3A%20%0A	Headers are optional, but often include subject=; body= can be used to pre-fill the body of the message.
mid	Referencing SMTP/MIME messages, or parts of messages.	RFC 2111 RFC 2392	mid:<message-id>[/<content-id>]	(See also cid:)
modem	modem	RFC 2806		Seems to be deprecated in RFC 3966 in favour of tel:
msrp msrps	Message Session Relay Protocol	RFC 4975
mtqp	Message Tracking Query Protocol	RFC 3887
mupdate	Mailbox Update Protocol	RFC 3656
news	(Usenet) newsgroups and postings	RFC 1738 RFC 5538	news:<newsgroupname> or news:<message-id>	References a particular resource, regardless of location.
nfs	Network File System resources	RFC 2224	generic syntax
nntp	Usenet NNTP	RFC 1738 RFC 5538	nntp://<host>:<port>/<newsgroup-name>/<article-number>	Referencing a specific host is often less useful than referencing the resource generically, as NNTP servers are not always publicly accessible
opaquelocktoken	opaquelocktoken	RFC 2518 RFC 4918
pop	Accessing mailbox through POP3	RFC 2384	pop://[<user>[;AUTH=<auth>]@]<host>[:<port>]
pres	Used in Common Profile for Presence (CPP) to identify presence	RFC 3859	pres:<address>[?<header1>=<value1>[&<header2>=<value2>]]	Similar to "mailto:"
prospero	Prospero Directory Service	RFC 1738 RFC 4157		Listed as "Historical" by IANA.
rsync	rsync	RFC 5781	rsync://<host>[:<port>]/<path>
rtsp	Real Time Streaming Protocol	RFC 2326
service		RFC 2609
shttp	Secure HTTP	RFC 2660		Largely superseded by HTTPS.
sieve	ManageSieve protocol	RFC 5804
sip	Used with Session Initiation Protocol (SIP)	RFC 2543 RFC 3969 RFC 3261	sip:<user>[:<password>]@<host>[:<port>][;<uri-parameters>][?<headers>] examples: sip:alice@atlanta.com?subject=project%20x&priority=urgent sip:+1-212-555-1212:1234@gateway.com;user=phone
sips	Secure equivalent of sip	RFC 3969 RFC 3261	sips:<user>[:<password>]@<host>[:<port>][;<uri-parameters>][?<headers>]
sms	Interact with SMS capable devices for composing and sending messages.	RFC 5724	sms:<phone number>?<action> examples: sms:+15105550101?body=hello%20there sms:+15105550101,+15105550102?body=hello%20there	Should be used as a subset to the tel: schema.
snmp	Simple Network Management Protocol	RFC 4088	snmp://[user@]host[:port][/[<context>[;<contextEngineID>]][/<oid>]] examples: snmp://example.com//1.3.6.1.2.1.1.3+ snmp://tester5@example.com:8161/bridge1;800002b804616263
soap.beep soap.beeps		RFC 3288 RFC 4227
tag	Tag URI	RFC 4151	tag:<email/domainname>,<date>:<Item>	Represented entities do not necessarily have to be accessible electronically.
tel	Used for telephone numbers	RFC 5341 RFC 3966 RFC 2806	tel:<phonenumber>
telnet	Used with telnet	RFC 1738 RFC 4248	telnet://<user>:<password>@<host>[:<port>/]
tftp	Trivial File Transfer Protocol	RFC 3617
thismessage	multipart/related relative reference resolution	RFC 2557
tip	Transaction Internet Protocol	RFC 2371
tv	TV Broadcasts	RFC 2838
urn	Uniform Resource Names	RFC 2141	urn:<namespace>:<specificpart>
vemmi	Versatile Multimedia Interface	RFC 2122
wais	Used with Wide area information server (WAIS)	RFC 1738 RFC 4156	wais://<host>:<port>/<database>[?<search>] or wais://<host>:<port>/<database>/<wtype>/<wpath>	Listed as "Historical" by IANA.
xmlrpc.beep xmlrpc.beeps		RFC 3529
xmpp	XMPP	RFC 4622 RFC 5122	xmpp:<user>@<host>[:<port>]/[<resource>][?<query>]
z39.50r	Z39.50 retrieval	RFC 2056	z39.50r://<host>[:<port>]/<database>?<docid>[;esn=<elementset>][;rs=<recordsyntax>]
z39.50s	Z39.50 session	RFC 2056	z39.50s://<host>[:<port>]/[<database>][?<docid>][;esn=<elementset>][;rs=<recordsyntax>]

Unofficial but common URI schemes

Scheme	Purpose	Defined by	General format	Notes
about	Displaying product information and internal information	IETF Draft	See about URI scheme for more details.	Widely used by web browsers, sometimes even providing interactive resources. The Opera web browser uses opera: instead.
adiumxtra	Direct installation of Adium Xtras (plugins).	The Adium Team	adiumxtra://www.adiumxtras.com/download/0000	0000 refers to a specific Xtra
aim	Controlling AOL Instant Messenger.	AOL	aim:<function>?<parameters>	Functions include goim, addbuddy, and buddyicon.
apt	Experimental method of installing software using APT.		apt:<package name>	Commonly found on websites which contain Debian software repositories.
afp	Accessing Apple Filing Protocol shares	IETF Draft	over TCP/IP: afp://[<user>@]<host>[:<port>][/[<path>]] over AppleTalk: afp:/at/[<user>@]<host>[:<zone>][/]
aw	Link to an Active Worlds world	Activeworlds Inc.	aw://<worldserver host>:<worldserver port>/<worldname>	Mostly found in HTTP referers when users open a website from within a Active Worlds world.
bitcoin	Send money to a Bitcoin address	Bitcoin URI Scheme	bitcoin:<address>[?[amount=<size>][&][label=<label>][&][message=<message>]]
bolo	Join an existing bolo game.		bolo://<hostname>/	Mostly passed via IRC or via tracker servers.
callto	Launching Skype call (+And in Hungary the KLIP Software call too) (unofficial; see also skype:)	Skype	callto:<screenname> or callto:<phonenumber> [2]	Introduced with Microsoft NetMeeting. Works with current version of Skype with Firefox, Internet Explorer and Safari
chrome	Specifies user interfaces built using XUL in Mozilla-based browsers.	Mozilla	chrome://<package>/<section>/<path> (Where <section> is either "content", "skin" or "locale")	Works only in Mozilla-based browsers such as Firefox, SeaMonkey and Netscape. Not related to the Google Chrome browser.
coap	Accessing Constrained Application Protocol (CoAP) resources.	IETF Draft	coap://<host>[:<port>]/<path>[?<query>]	Identify CoAP resources and provide a means of locating the resource.
content	Accessing an Android content provider.	Open Handset Alliance	content://provider/<path>	Performs a query on an Android Content Provider
cvs	Provides a link to a Concurrent Versions System (CVS) Repository	Concurrent Versions System	cvs://<method:logindetails>@<repository>/<modulepath>;[date=date to retrieve | tag=tag to retrieve]
doi	Digital object identifier, a digital identifier for any object of intellectual property.	IETF Draft	doi:10.<publisher number>/<suffix> Example: doi:10.1000/182	Used e.g. for most scientific publications. Can be resolved via HTTP (transormed into an URL) by appending http://dx.doi.org/ or http://hdl.handle.net/ in front.
ed2k	Resources available using the eDonkey2000 network	eDonkey2000	ed2k://|file|<filename>|<size of file>|<hash of file>|/ or ed2k://|server|<host>|<port>|/	Links to servers are also possible, as are additional parameters. Official documentation from Template:Wayback
Facetime	FaceTime is a video conferencing software developed by Apple for iPhone 4, the fourth generation iPod Touch, and computers running Mac OS X.	Apple Inc.	facetime://<address>|<MSISDN>|<mobile number> example: facetime://+19995551234	Apple has not published documentation on this protocol yet.
feed	web feed subscription		feed:<absolute_uri> or feed://<hierarchical part> examples: feed://example.com/rss.xml feed:https://example.com/rss.xml	See Feed URI scheme for a detailed overview of common implementations, supported software, and critics.
finger	Querying user information using the Finger protocol	IETF Draft	finger://host[:port][/<request>]
fish	Accessing another computer's files using the SSH protocol	fish KDE kioslave	fish://[<username>[:<password>]@]<hostname>[:<port>]	See Files transferred over shell protocol for details about the protocol.
git	Provides a link to a GIT repository	Git	Github example: git://github.com/user/project-name.git
gg	Starting chat with Gadu-Gadu user	Gadu-Gadu	gg:<userid>
gizmoproject	Gizmo5 calling link.		gizmoproject://call?id=<gizmo_id>	May use sip:// instead of gizmoproject:// in recent versions of Gizmo5.
gtalk	Start a chat with a Google Talk user	Google Talk	gtalk:chat?jid=example@gmail.com	See Google Talk, XMPP, and http://juberti.blogspot.com/2006/11/gtalk-uri.html for more information
irc	Connecting to an Internet Relay Chat server to join a channel.	IETF Draft Old IETF Draft	irc://<host>[:<port>]/[<channel>[?<password>]]	Assuming the client knows a server associated with the name, "host" may optionally be an IRC network name.
ircs	Secure equivalent of irc	IETF Draft	ircs://<host>[:<port>]/[<channel>[?<password>]]	See irc
irc6	IPv6 equivalent of irc		irc6://<host>[:<port>]/[<channel>[?<password>]]	See irc
itms	Used for connecting to the iTunes Music Store	Apple Inc	itms:
jar	Compressed archive member	Java API	jar:<url>!/[<entry>]	Works for any ZIP based file.
javascript	Execute JavaScript code	IETF Draft	javascript:<javascript to execute>	Works in any modern browser.
keyparc	Keyparc encrypt/decrypt resource.	Bloombase	keyparc://encrypt/<username>/<uri> or keyparc://decrypt/<username>/<uri>
lastfm	Connecting to a radio stream from Last.fm.	Last.fm	lastfm://<radio_stream> or lastfm://globaltags/<genre> or lastfm://user/<username>/<stuff>
ldaps	Secure equivalent of ldap	Old version of IETF Draft	ldaps://[<host>[:<port>]][/<dn> [?[<attributes>][?[<scope>][?[<filter>][?<extensions>]]]]]	Not an IETF standard, but commonly used in applications.
magnet	"magnet links"	Magnet-URI Project	magnet:?xt=urn:sha1:<hash of file>&dn=<display name> (other parameters are also possible)	Used by various peer-to-peer clients, usually providing the hash of a file to be located on the network.
maps	"map links"		maps:q=<physical location>	Some mobile web browsers will launch a dedicated mapping application. See also "geo:" (RFC 5870)
mms	Windows streaming media		mms://<host>:<port>/<path>	Used by Windows Media Player to stream audio and/or video.
msnim	Adding a contact, or starting a conversation in Windows Live Messenger	Windows Live Messenger	Add a contact to the buddy list msnim:add?contact=nada@example.com Start a conversation with a contact msnim:chat?contact=nada@example.com Start a voice conversation with a contact msnim:voice?contact=nada@example.com Start a video conversation with a contact msnim:video?contact=nada@example.com	Can be invoked from a web page or via a run command or an Internet Explorer browser URL (won't work with Firefox 2.0.0.8). For web pages use this HTML: <a href="chat?contact=nada@example.com">Click to chat!</a>
mumble	Joining a server.	Mumble (software)	mumble://[username[:password]@]<address>[:port]/[channelpath]?version=<serverversion>[&title=<servername>][&url=<serverurl>]	Official documentation from Mumble website
mvn	Access Apache Maven repository artifacts	OPS4J	mvn:org.ops4j.pax.web.bundles/service/0.2.0-SNAPSHOT mvn:http://user:password@repository.ops4j.org/maven2!org.ops4j.pax.web.bundles/service/0.2.0
notes	Open a Lotus Notes document or database	Lotus Notes	notes://<address>	Used by IBM Lotus Notes to refer to documents and databases stored within the Lotus Notes system. When clicked in a browser on a computer with Lotus Notes client installed, Notes will open the document link as if a Notes DocLink were clicked within Notes.
palm	Used to designate system services in HP webOS applications	HP webOS	palm:<servicename>[/<method>]]/	Official documentation from HP webOS Services Overview
paparazzi	Used to launch and automatically take a screen shot using the application "Paparazzi!" (Mac only)	Derailer	paparazzi:[<options>]http:[//<host>[:[<port>][<transport>]]/	Official documentation from the Paparazzi! website
psyc	Used to identify or locate a person, group, place or a service and specify its ability to communicate	PSYC	psyc:[//<host>[:[<port>][<transport>]]/[<object-name>][#<channel-name>]	-
rmi	Look up a Java object in an RMI registry.	Sun	rmi://<host>[:<port>]/<object-name>	URI scheme understood by JNDI. Can be used to lookup a remote Java object within an RMI registry (typically for the purposes of RMI on that object). Host/port in the URI are of the rmiregistry process, not the remote object.
rtmp	Real Time Messaging Protocol	Adobe Systems	rtmp://<host>/<application>/<media>	URI schema used to connect to Adobe Flash Media Server.
secondlife	Open the Map floater in Second Life application to teleport the resident to the location.	Linden Lab	secondlife://<region name>/<x position>/<y position>/<z position>	Used by SLurl.com. Knowledge base article.
sgn	Social Graph Node Mapper	Google	example: sgn://social-network.example.com/?ident=bob	Official documentation from sgnodemapper project.
skype	Launching Skype call (unofficial; see also callto:)	Skype	skype:<username|phonenumber>[?[add|call|chat|sendfile|userinfo]]	Official documentation from Skype website.
spotify	Load a track, album, artist, search, or playlist in Spotify	Spotify	spotify:<artist|album|track>:<id> or spotify:search:<text> or spotify:user:<username>:playlist:<id> example: spotify:track:2jCnn1QPQ3E8ExtLe6INsx	Informally specified in Spotify official blog post by CTO Andreas Ehn.
ssh	SSH connections (like telnet:) and	IETF Draft	ssh://[<user>[;fingerprint=<host-key fingerprint>]@]<host>[:<port>]
sftp	SFTP file transfers (not be to confused with FTPS (FTP/SSL))	IETF Draft	sftp://[<user>[;fingerprint=<host-key fingerprint>]@]<host>[:<port>]/<path>/<file>
smb	Accessing SMB/CIFS shares	IETF Draft	smb://[<user>@]<host>[:<port>][/[<path>]][?<param1>=<value1>[;<param2>=<value2>]] or smb://[<user>@]<workgroup>[:<port>][/]
soldat	Joining servers	Soldat	soldat://<host>:<port>/[password] example: soldat://127.0.0.1:23073/thatssecret!	Official note in Manual
steam	Interact with Steam: install apps, purchase games, run games, etc.	Steam, Valve Corporation	steam:<command line arguments> or steam://<action>/<id, addon, IP, hostname, etc.>	Official documentation from Valve Developer Community website
svn	Provides a link to a Subversion (SVN) source control repository	Subversion (software)	svn[+ssh]://<logindetails>@<repository><:port>/<modulepath>
teamspeak	Joining a server.	TeamSpeak	teamspeak://<server>[:<port>]/[?<parameter1>=<value1>[&<parameter2>=<value2>]]	Official documentation from TeamSpeak Website
things	Send a to-do to Things.	Cultured Code	things:add?title=Buy%20milk&notes=Low%20fat&dueDate=2011-12-24	This URI scheme works on Mac OS & iOS, providing Things by Cultured Code is installed.
unreal	Joining servers	Unreal	unreal://<server>[:<port>]/	Unreal legacy "protocol"
ut2004	Joining servers	Unreal Tournament 2004	ut2004://<server>[:<port>][/<map>?<options>]	Documentation from Unreal Developer Network
ventrilo	Joining a server.	Ventrilo	ventrilo://<server>[:<port>]/[?<parameter1>=<value1>[&<parameter2>=<value2>]]	Official documentation from Ventrilo Website
view-source	Shows a web page as code 'in the raw'.	IETF Draft	view-source:<URI> example: view-source:http://en.wikipedia.org/wiki/URI_scheme	See view-source URI scheme for details.
webcal	Subscribing to calendars in iCalendar format	iCalendar	webcal://<hierarchical part> example: webcal://example.com/calendar.ics	HTTP as a transport protocol is assumed. See Webcal for details.
ws wss	WebSocket protocol	IETF Draft	ws:<hierarchical part>
wtai	Wireless Telephony Application Interface	WAP Forum	wtai://wp/mc/+18165551212	See Application Protocol Wireless Application Environment Specification Version 1.1 for details.
wyciwyg	What You Cache Is What You Get WYCIWYG	Mozilla	wyciwyg://<URI>	See WYCIWYG for details.
xfire	Adding friends and servers, joining servers, changing status text.	Xfire	xfire:<function>[?<parameter1>=<value1>[&<parameter2>=<value2>]]	Official documentation from Xfire website
xri	eXtensible Resource Identifier (XRI)	OASIS XRI Technical Committee	xri://<authority>[/[<path>]][?<query>][#fragment]	Official documentation from OASIS XRI Technical Committee
ymsgr	Sending an instant message to a Yahoo! Contact.	Yahoo! Messenger	ymsgr:sendIM?<screenname>

External links

• Official IANA Registry of URI Schemes
• More information, including many more schemes