Meet WOFF, The Standard Web Font Format

On April 8, 2010, Mozilla, Opera and Microsoft submitted the WOFF File Format 1.0 specification to the W3C. The submission was published on Monday, April 19 at

Browser vendors and a growing number of type foundries now agree on a common encoding format for web fonts, thus closing an era of cross-browser incompatibility that began when IE4 and Netscape 4 first added support for downloadable fonts in 1997.

At the time, both Microsoft and Netscape implemented incompatible proprietary solutions. Netscape supported and later dropped Bitstream’s Portable Font Resource (PFR) format.  Internet Explorer’s Embedded Open Type (EOT) supported the sub-setting and compression of fonts, as well as the definition of the origin policy for the font resource within the EOT file itself. Some font vendors have licensed their fonts for web use under EOT.

Ten years later, Apple added support for raw font linking to WebKit and Safari, allowing web authors to refer to raw TrueType or OpenType font files from their CSS stylesheets. Firefox and Opera followed but use of the feature was in practice limited to free fonts and specialist font obfuscation services like Typekit as font vendors were extremely reluctant to allow their intellectual property to be posted as-is on web servers. The typically large size of font files and the challenges involved in compressing HTTP responses for all users added practical challenges.

In March 2008, Microsoft submitted EOT for standardization to the W3C. Despite a large existing EOT-compatible IE installed base, a number of issues prevented consensus from emerging on the suitability of Microsoft’s format as a web font standard. At the W3C’s Technical Plenary that year, Microsoft indicated that a solution type foundries were comfortable with was essential to maximize author choice. In the summer of last year, such a solution emerged from a proposal by type designers Tal Leming and Erik van Blokland and Mozilla’s Jonathan Kew. The Web Open Font Format (WOFF) - an open, compressed encoding for sfnt-based font resources - was born.

The new format’s specification is a deliverable of the newly chartered Fonts Working Group on which browser vendors, type foundries and designers are represented. We are excited by some of the initial feedback to this announcement and look forward to contributing to the Working Group to advance the state of web font interoperability.

Sylvain Galineau
Program Manger

Update 5:25pm: small edits for clarity in the third paragraph.