Web Open Font Format

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Web Open Font Format
Filename extension
  • .woff
  • .woff2
Internet media type
  • font/woff
  • font/woff2
  • application/font-woff (deprecated)[1][2]
Magic number
  • 77 4F 46 46 ("wOFF" in ASCII)
  • 77 4F 46 32 ("wOF2" in ASCII)
Developed byW3C
Type of formatFont file
Container forSFNT fonts

The Web Open Font Format (WOFF) is a font format for use in web pages. WOFF files are OpenType or TrueType fonts, with format-specific compression applied and additional XML metadata added. The two primary goals are to first distinguish font files intended for use as web fonts from fonts files intended for use in desktop applications via local installation, and second to reduce web font latency when fonts are transferred from a server to a client over a network connection.


Version 1 was developed during 2009[3] and became a World Wide Web Consortium (W3C) Recommendation in 2012.[4]

The WOFF specification was written by Jonathan Kew, Tal Leming, and Erik van Blokland,[3] with reference conversion code written by Jonathan Kew.[5] Following the submission of WOFF by the Mozilla Foundation, Opera Software and Microsoft in April 2010,[6][7] the W3C commented that it expected WOFF soon to become the "single, interoperable [font] format" supported by all browsers.[8] The W3C published WOFF as a working draft in July,[9][10] and it became a W3C Recommendation in December that year.

WOFF 2.0, with reference code provided by Google,[11] has an improved compression scheme, using Brotli for byte-level compression, and became a W3C Recommendation in March 2018.[12]


WOFF is a wrapper containing SFNT-based fonts (TrueType or OpenType) that have been compressed using a WOFF-specific encoding tool so they can be embedded in a Web page.[3] WOFF Version 1 uses the widely available zlib compression (specifically, the compress2 function),[3] typically resulting in a file size reduction for TrueType files of over 40%.[13] Since OpenType CFF files (with PostScript glyph outlines) are already compressed, their reduction is typically smaller.[14]

Vendor support[edit]

Each version of the format has received the backing of many font vendors, also known as type foundries[15], and has been supported by all major browsers:

WOFF 2.0, based on the Brotli compression algorithm and other improvements over WOFF 1.0 giving more than 30% reduction in file size, is supported in

  • Google Chrome (since version 36),[26]
  • Edge (since version 14),[27]
  • Opera (since version 26),[28]
  • Firefox (since version 35)[29]
  • Safari (since version 10).[30]

Some browsers enforce a same-origin policy, preventing WOFF fonts from being used across different domains. This restriction is part of the CSS 3 Fonts module,[31] where it applies to all font formats and can be overridden by the server providing the font.

Some servers may require the manual addition of WOFF's MIME type to serve the files correctly.[32] Since February 2017, the proper MIME type is font/woff for WOFF 1.0 and font/woff2 for WOFF 2.0[1][2]. Prior to February 2017, the standard MIME type for WOFF 1.0 was application/font-woff, and some applications may still use the old type, though it is now deprecated.[1]

See also[edit]


  1. ^ a b c "Media Types". IANA. 2017-10-12. Retrieved 2017-10-17.
  2. ^ a b "The "font" Top-Level Media Type". IETF. February 2017. RFC 8081. Retrieved 2017-10-17.
  3. ^ a b c d Kew (Mozilla), Jonathan; Leming (Type Supply), Tal; van Blokland (LettError), Erik (2009-10-23), WOFF File Format (draft of 2009-10-23), Mozilla Foundation, retrieved 2010-01-30
  4. ^ WOFF File Format 1.0
  5. ^ WOFF conversion reference code, retrieved May 8, 2016
  6. ^ WOFF File Format 1.0 Submission Request to W3C
  7. ^ Galineau, Sylvain (2010-04-23), Meet WOFF, The Standard Web Font Format, Microsoft
  8. ^ Team Comment on "WOFF File Format 1.0" Submission
  9. ^ WOFF - Now loading fonts on websites, The H, 2010-07-28
  10. ^ Buckler, Craig (2010-08-17), W3C Backs the WOFF WebFont Standard, SitePoint
  11. ^ Reference WOFF2 generation code, retrieved May 8, 2016
  12. ^ W3C: WOFF File Format 2.0
  13. ^ Stefanov, Stoyan (2009-10-20), @font-face gzipping - take II, PHPied.com, retrieved 2010-01-30
  14. ^ http://blog.typekit.com/2010/12/08/type-rendering-font-outlines-and-file-formats/
  15. ^ Wardle, Tiffany (2009-07-16), Typegirl - Most of the important foundries are supporting #webfont, tumblr, retrieved 2010-02-05
  16. ^ Shapiro, Melissa (2009-10-20), Mozilla Supports Web Open Font Format, Mozilla Foundation, retrieved 2010-02-05
  17. ^ Colyer, Matt (2010-09-21), Typekit adds Chrome 6 WOFF support, Typekit
  18. ^ Hachamovitch, Dean (2010-06-23), HTML5, Native: Third IE9 Platform Preview Available for Developers, Microsoft
  19. ^ KDE SVN Revision 1088984, KDE Bugzilla, 2010-02-12, retrieved 2011-10-14
  20. ^ A first glimpse at Opera 11.10 "Barracuda", Opera Software, 2011-02-17, retrieved 2011-02-17
  21. ^ Web specifications support in Opera Presto 2.7, Opera
  22. ^ Safari Features, Apple, 2011-06-06, retrieved 2011-10-14
  23. ^ Safari 5.1 Changelog, FileHippo.com, retrieved 2011-10-14
  24. ^ Bug 38217 - [chromium] Add WOFF support, WebKit
  25. ^ Bug 31302 - Add WOFF support for @font-face, WebKit
  26. ^ Chromium 36 Release Notes, Google
  27. ^ Speed up page load with WOFF 2.0 fonts in Microsoft Edge, Microsoft
  28. ^ Opera 26 Release Notes, Opera Software ASA
  29. ^ Firefox 35 Release Notes, Mozilla Developer Network
  30. ^ What's new in Safari, Apple
  31. ^ CSS Fonts Module Level 3
  32. ^ "Webfonts are not loading in Firefox". Fontspring. Retrieved 2013-01-01.

External links[edit]