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 first to 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.


The first draft of WOFF 1 was published in 2009 by Jonathan Kew, Tal Leming, and Erik van Blokland,[3] with reference conversion code written by Jonathan Kew.[4] Following the submission of WOFF to the World Wide Web Consortium (W3C) by the Mozilla Foundation, Opera Software and Microsoft in April 2010,[5][6] the W3C commented that it expected WOFF to soon become the "single, interoperable [font] format" supported by all browsers.[7] The W3C published WOFF as a working draft in July 2010.[8][9] The final draft was published as a W3C Recommendation on 13 December 2012.[10]

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]

Each version of the format has received the backing of many type foundries.[13]


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.[14] WOFF Version 1 uses the widely available zlib compression (specifically, the compress2 function),[14] typically resulting in a file size reduction for TrueType files of over 40%.[15] Since OpenType CFF files (with PostScript glyph outlines) are already compressed, their reduction is typically smaller.[16]

Browser support

Major web browsers support WOFF:

WOFF 2.0 is supported in:

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,[32] 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.[33] 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


  1. ^ a b c "Media Types". IANA. 2017-10-12. Retrieved 2017-10-17.
  2. ^ a b Lilley, Chris (February 2017). "The "font" Top-Level Media Type". IETF. doi:10.17487/RFC8081. RFC 8081. Retrieved 2017-10-17. ((cite journal)): Cite journal requires |journal= (help)
  3. ^ Kew (Mozilla), Jonathan; Leming (Type Supply), Tal; van Blokland (LettError), Erik (2009-10-23), WOFF File Format (draft of 2009-10-23), Mozilla Foundation, archived from the original on 2010-03-09, retrieved 2010-01-30
  4. ^ WOFF conversion reference code, retrieved May 8, 2016
  5. ^ WOFF File Format 1.0 Submission Request to W3C
  6. ^ Galineau, Sylvain (2010-04-23), Meet WOFF, The Standard Web Font Format, Microsoft, archived from the original on 29 May 2010
  7. ^ Team Comment on "WOFF File Format 1.0" Submission
  8. ^ WOFF - Now loading fonts on websites, The H, 2010-07-28
  9. ^ Buckler, Craig (2010-08-17), W3C Backs the WOFF WebFont Standard, SitePoint
  10. ^ "WOFF File Format 1.0". www.w3.org. Retrieved 2019-08-31.
  11. ^ Reference WOFF2 generation code, retrieved May 8, 2016
  12. ^ W3C: WOFF File Format 2.0
  13. ^ Wardle, Tiffany (2009-07-16), "Most of the important foundries are supporting #webfont", Typegirl, retrieved 2010-02-05 – via tumblr
  14. ^ a b Kew (Mozilla), Jonathan; Leming (Type Supply), Tal; van Blokland (LettError), Erik (2009-10-23), WOFF File Format (draft of 2009-10-23), Mozilla Foundation, archived from the original on 2010-03-09, retrieved 2010-01-30
  15. ^ Stefanov, Stoyan (2009-10-20), @font-face gzipping - take II, PHPied.com, retrieved 2010-01-30
  16. ^ "The Typekit Blog | Type rendering: Font outlines and file formats".
  17. ^ Shapiro, Melissa (2009-10-20), Mozilla Supports Web Open Font Format, Mozilla Foundation, retrieved 2010-02-05
  18. ^ Colyer, Matt (2010-09-21), Typekit adds Chrome 6 WOFF support, Typekit
  19. ^ Hachamovitch, Dean (2010-06-23), HTML5, Native: Third IE9 Platform Preview Available for Developers, Microsoft
  20. ^ KDE SVN Revision 1088984, KDE Bugzilla, 2010-02-12, retrieved 2011-10-14
  21. ^ A first glimpse at Opera 11.10 "Barracuda", Opera Software, 2011-02-17, retrieved 2011-02-17
  22. ^ Web specifications support in Opera Presto 2.7, Opera
  23. ^ Safari Features, Apple, 2011-06-06, retrieved 2011-10-14
  24. ^ Safari 5.1 Changelog, FileHippo.com, retrieved 2011-10-14
  25. ^ Bug 38217 - [chromium] Add WOFF support, WebKit
  26. ^ Bug 31302 - Add WOFF support for @font-face, WebKit
  27. ^ Chromium 36 Release Notes, Google
  28. ^ Speed up page load with WOFF 2.0 fonts in Microsoft Edge, Microsoft, 3 May 2016
  29. ^ Opera 26 Release Notes, Opera Software ASA
  30. ^ Firefox 35 Release Notes, Mozilla Developer Network
  31. ^ What's new in Safari, Apple
  32. ^ CSS Fonts Module Level 3
  33. ^ "Webfonts are not loading in Firefox". Fontspring. Retrieved 2013-01-01.