Font file types: every font extension, explained

Fonts have been digital for forty years, and every era left its file format behind like a shell. The result is a downloads folder that can confront you with a dozen extensions — .ttf, .otf, .woff2, .pfb, .eot — with no indication of which are fonts, which are fossils, and which aren’t fonts at all. This is the complete map: every font file type you’re likely to meet, what it is, and what to do with it. (If you only need the two common ones, our OTF vs TTF explainer is the short version.)

The formats you’ll actually meet

Nine cards cover nearly every font file in the wild. Two things worth noticing in them. First, the modern world runs on just two installable formats — .ttf and .otf — plus two web-only ones, .woff and .woff2. Everything else on the shelf is history or plumbing. Second, the extensions lie by omission: they tell you the container, not the contents, which matters more than most people realize.

Same extension, different insides

The hardest idea in font formats is that the ending is not the whole story:

• An .otf can be two different fonts inside. OpenType is a container with two outline engines: TrueType-style (quadratic curves) or CFF (PostScript-style cubic curves). Two .otf files can be built completely differently under the hood. A .ttf, by contrast, is always TrueType-flavored — and can still carry OpenType’s layout features, which is why the extension can’t tell you what a font can do.
• Color fonts hide in ordinary files. Multicolor type — emoji fonts, ornate display faces — is stored as extra tables inside regular .otf/.ttf files. There are several rival color technologies in there (Google’s bitmap CBDT, Apple’s sbix, Microsoft’s layered COLR, and the SVG table), which is why a color font may sing in one program and fall back to plain black in another.
• Variable fonts hide too. Since 2016, a single .ttf or .otf can contain a whole family’s worth of weights and widths as adjustable axes. Same extension, new superpower — the file name (sometimes with “Variable” or bracketed axis ranges) is the only outward clue.

The web formats, and why they’re smaller

WOFF and WOFF2 exist because websites send fonts to browsers, and bytes are time. Both are the same fonts you’d install, wrapped in compression. WOFF2’s Brotli compression usually wins by a wide enough margin that it’s the only web format a new site needs:

Never try to install a .woff or .woff2 on a desktop or phone — they aren’t broken, they’re just packaged for browsers. Go back to the source and get the .ttf or .otf of the same font.

The deep cuts

Beyond the nine cards, a long tail of extensions survives in old archives, Linux systems, and specialist corners:

And two companions that are not fonts by themselves: .afm (Adobe Font Metrics — a text file of widths and kerning that accompanied Type 1 fonts) and .pfm (its Windows metrics twin). A folder holding only an .afm is a font missing its other half.

Source files: fonts that aren’t fonts yet

Designers’ working files have extensions too, and archives sometimes leak them into downloads:

• .ufo — Unified Font Object, the open source format font editors exchange (a folder of XML, really).
• .sfd — FontForge’s native Spline Font Database.
• .glyphs — the Glyphs app’s source format.
• .fea — an OpenType feature file: plain text describing ligatures and alternates, compiled into a font later.

None of these can be installed; they’re the kitchen, not the meal. If a download contains one, the installable .ttf/.otf is usually alongside it — or the designer published the source by mistake instead of the font.

So which file do I install?

• .ttf or .otf — yes. (Both offered? Take the OTF, usually.)
• .ttc or .otc — yes, your system unpacks the collection itself.
• .woff / .woff2 — no; those are for websites. Find the desktop version.
• .pfb, .fon, .eot, .svg, anything in the deep-cuts table — not on a modern system. The living move is to find the same typeface reissued in OpenType — most classic faces have been — or convert the file with a tool like FontForge if the license allows.
• .zip — never a font, always a container. Unpack it first; our install guides start there.

The map is bigger than the territory you need. Day to day, fonts are two extensions and a zip — everything else on this page is the archaeology of how they got that simple.