W3C | Submissions

Status: Team confidential – under team review

Team Comment on the Embedded OpenType (.EOT) Font Format Submission

W3C is pleased to receive the Embedded OpenType (.EOT) Font Format Submission from Microsoft Corp. and Monotype Imaging.

What is EOT?

EOT is a wrapper around OpenType font data to provide certain functionality that would be difficult or impossible with OpenType font files on their own. In particular, it allows subsetting of fonts (omitting unnecessary characters) without causing confusion between full and subsetted fonts of the same name, it provides compression through Monotype's MicroType® Express algorithm, and it allows binding of fonts to particular Web pages, in case the font's copyright license doesn't allow unlimited use. It's that latter functionality that explains the name “embedded.”


The EOT format can be, and indeed has been, used for many kinds of documents and applications on the Web. All that is required is that the document/application can refer to an external font by URL and that it has a URL itself. The most interesting aspect for W3C is that it is a complement to the WebFonts technology, which was developed for CSS and is also used by SVG.

WebFonts (a.k.a., “@font-face”) is the glue that translates font names to URLs inside a CSS or SVG file, but it doesn't provide any actual font data, nor does it handle “embedding” in the sense of limiting a font to a known set of documents, as required by many current font licenses.

A typical use of EOT for an HTML page would be as follows: a LINK element in the page points to a CSS style sheet, an @font-face rule in the style sheet points to an EOT file and the EOT file links back to the HTML page. When this circle is closed, it means the font may be used for that page.

The aspect of limiting a font to one or more pages chosen by the author, rather than allowing it to be used anywhere, has been controversial in discussions until now. The argument is that it is not for technology to limit the choices in what is essentially a legal problem. For example, Web pages don't require images to have a link back to the document they are used in, although images are copyrightable, too.

Nevertheless, we believe EOT can be a step forward in the use of fonts on the Web, for two reasons:

  1. At the moment, a large part of the font industry will not license its best fonts for use on the Web in any of the current font formats, but they have indicated that they will allow fonts to be used if distributed in the form of EOT. That means that many font uses become possible that were not possible before.
  2. EOT can link back to documents, but it doesn't have to. The advantages of EOT (subsetting & compression) are available even for fonts that can be freely distributed. This was one of the conditions under which the W3C team accepted to consider EOT for further development and an eventual W3C Recommendation for EOT will have to make clear how this works.

Note that EOT, as a wrapper for OpenType, is of limited use without OpenType. Software that implements OpenType may or may not require a license.

Next step

W3C plans to submit a proposal to the W3C members for a working group whose goal is to try and develop EOT into a W3C Recommendation.

Bert Bos