What is EOT? The Embedded OpenType Web Font Format Explained
Microsoft's legacy web font format for embedding TrueType and OpenType fonts in web pages.
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What is EOT?
EOT, short for Embedded OpenType, is a compact font file format developed by Microsoft to allow TrueType and OpenType fonts to be embedded in and downloaded for web pages. It was introduced with Internet Explorer to enable web typography before standard web font formats existed.
An EOT file wraps an OpenType or TrueType font with additional headers, optional subsetting to include only needed glyphs, and optional compression using Monotype's MicroType Express technology. EOT files can be bound to specific web pages or domains as a form of usage restriction. Microsoft and Monotype Imaging submitted the format to the W3C in 2008, but the W3C ultimately chose WOFF as its recommended web font format.
How EOT Works
An EOT file prepends a binary header to an embedded OpenType or TrueType font. The header records the font's family and style names, the size of the embedded data, and an optional list of root strings identifying the web pages or domains permitted to use the font.[1] The font itself may be subsetted to include only the glyphs a page needs and optionally compressed with MicroType Express.[2]
History and Standardization
Microsoft created EOT for Internet Explorer to enable downloadable web fonts long before a cross-browser standard existed, and submitted the format to the W3C in 2008.[1] The W3C did not adopt it as a recommendation, instead standardizing WOFF.[2]
Limitations and Legacy
The format's root-string binding offered only weak usage restriction and was not honored outside Internet Explorer, while EOT support was effectively limited to that browser.[2] Registered under application/vnd.ms-fontobject, it is now largely obsolete, retained mainly for legacy IE compatibility.[3]
MKV Technical Specifications
EOT vs Other Font Formats
| Feature | EOT | WOFF | TTF |
|---|---|---|---|
| Type | Outline (OpenType)[1] | Outline wrapper | Outline |
| Standardized by | Microsoft / W3C note[1] | W3C | Apple / ISO |
| Web-optimized | Legacy IE only[2] | Yes | Partial |
| Compression | Optional[3] | Yes | None |
| Best for | Old Internet Explorer | Modern web fonts | Desktop / web fallback |
EOT was an Internet Explorer-only web font format now superseded by WOFF and WOFF2.
Advantages & Disadvantages
Advantages
It enabled custom fonts on web pages in Internet Explorer long before WOFF existed.
Fonts can be subset to include only the glyphs a page needs, reducing download size.
Supports Monotype's MicroType Express compression to shrink embedded font data.
Fonts can be tied to specific pages or domains, which font vendors used as a licensing safeguard.
Disadvantages
EOT is supported essentially only by old versions of Internet Explorer and not by modern browsers, including Edge.
WOFF and WOFF2 became the W3C-recommended standards, making EOT obsolete.
Creating EOT files requires specialized converters that are no longer commonly maintained.
Common Use Cases
EOT is now relevant mainly for legacy browser compatibility.
Legacy IE support | FileFormer
Web font stacks historically included an EOT file to serve older Internet Explorer versions.
Archival web projects | FileFormer
Maintaining or restoring older sites may require handling existing EOT font assets.
Cross-browser font kits | FileFormer
Older @font-face kits bundled EOT alongside WOFF, TTF, and SVG for maximum reach.
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Try Font Converter FreeFrequently Asked Questions
Is EOT still used today?
Rarely. It is a legacy format supported only by old Internet Explorer, and modern sites use WOFF or WOFF2 instead.
Who created EOT?
Microsoft developed it for Internet Explorer, and it was later submitted to the W3C together with Monotype Imaging.
What is the difference between EOT and WOFF?
Both embed fonts for the web, but WOFF is an open W3C standard supported by all modern browsers, while EOT is a proprietary Microsoft format limited to Internet Explorer.
Does EOT compress fonts?
It can. EOT optionally uses Monotype's MicroType Express compression and supports subsetting to reduce file size.
Should I still serve EOT files?
Only if you must support very old Internet Explorer versions; otherwise WOFF2 with WOFF fallback is sufficient.