What is an EOT file?

EOT is a binary format, meaningful only to a program that knows it. It is used for the web.

The extension is .eot, and the full name is Embedded OpenType. Both matter less than what the file can hold, which is what the rest of this page is about.

Microsoft published it in 1997.

A format that has been readable for that long is a format worth trusting with something you want back in ten years.

Reading it outside the vendor’s own software depends on work done by other people, usually by inspection rather than by documentation. That mostly works and occasionally does not, which is the reason to convert anything you intend to keep.

The people who made it have moved on, and support is being withdrawn rather than added. Anything still in this format is worth moving while the tools to move it are still around.

fonttools reads it, and so do most programs of the same kind.

If a file will not open, the format is rarely the problem — it is more often that the program predates it. Converting to something older is the reliable way past that, and it is what the rest of this site is for.

No browser reads it.

That is the single most common reason to convert it: not that the format is bad, but that the place you want to show the file cannot read it.

EOT is meant to be handed over rather than worked in. Editing one is possible and rarely pleasant; the sane approach is to change the source and export again.

The recurring complaints: support outside its home ground is uneven.

None of these is a reason to avoid the format. They are the things worth knowing before you are surprised by one, which is a different claim and a more useful one.

Microsoft published Embedded OpenType in 1997, years before any other browser could load a font from a web page. Internet Explorer could, and it would only load this — a compressed OpenType font with a list of domains baked into it, so that a font licensed for one site could not simply be lifted onto another.

That was the pitch: web fonts with a technical answer to the licensing objection. It never worked outside Internet Explorer, no other browser implemented it, and the domain restriction turned out to be more of an obstacle to the people paying for fonts than to anyone copying them.

For about a decade, every web font generator produced the same block: an EOT for old Internet Explorer, a WOFF for everything modern, a TTF for older Android, and an SVG font for early iOS. That stack was copied from tutorial to tutorial and it is still sitting in an enormous number of stylesheets.

All of it is now dead weight. WOFF2 alone covers every browser in use; the EOT line serves a browser Microsoft ended support for in 2022, on an operating system that has itself ended. Deleting it removes a file from your build and a request from the page, and breaks nothing that is not already broken.

An EOT can carry a list of the sites allowed to use it. Internet Explorer checked that list and refused the font on any other domain.

So a font recovered from an old site and moved to a new one may simply not load, with no error to explain it — and there is nothing to fix in the stylesheet, because the restriction is inside the font file. If a legacy EOT will not work on a new domain, this is why, and the answer is to go back to the original TTF or OTF rather than to fight the file.

This is genuinely the main reason to touch the format, and it is a rescue operation: an old site is being rebuilt, the original font files are gone, and what survives on the server is an EOT.

Underneath it is an OpenType font with compression and a header wrapped around it, so extracting a TTF or OTF is usually possible. Two things then need checking. Whether the extracted font is subset — many EOTs contain only the characters the old site used, and the missing ones will not reappear. And whether you are licensed to use it at all, because a font recovered from a website is not automatically a font you may deploy.

WOFF2, on its own, with no fallbacks. Every current browser reads it, it is the smallest of the options, and anything too old to understand it will fall back to a system font — an outcome that is perfectly acceptable and considerably better than serving four copies of a typeface so that a browser nobody uses gets its preferred one.

If a genuine requirement to support Internet Explorer 8 exists somewhere, in a locked-down internal system, the honest answer is still a system font for that browser. Maintaining an EOT pipeline in 2026 costs more than the typeface is worth to the three people affected.

Embedded OpenType tried to solve font licensing in the file. That approach lost, and the industry settled on solving it in the contract instead: a desktop licence covers installing a font on machines, and a web licence — priced separately, often by page views — covers serving it from a site.

Which means the rule that applies to a modern web font applied to the EOT too, and applies to whatever you extract from one. The technical restriction is gone; the licence is not, and it is the thing that actually decides whether a font may be used.

Embedded OpenType was a Microsoft format and Internet Explorer was the only browser that ever read it. From 1997 until Internet Explorer 9 it was the only way to use a custom typeface in that browser, which is why so much of the web's font markup carried a separate EOT branch for a decade.

Internet Explorer 9 added WOFF support in 2011 and the reason to produce EOT ended there. Microsoft ended support for Internet Explorer itself in 2022. A site still serving the format today is serving it to nothing, and the `@font-face` rule that references it is a request that will never usefully complete.