What is a TTF file?

TTF is a binary format, meaningful only to a program that knows it. It is used for typesetting.

The extension is .ttf, and the full name is TrueType Font. Both matter less than what the file can hold, which is what the rest of this page is about.

Apple published it in 1991. The specification is TrueType Reference Manual.

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

It is published in full, so anyone can implement it from the document rather than by inspection, which is why it turns up in so many programs and why files written twenty years ago still open. A published specification is not the same thing as a royalty-free one: where a format wraps a codec, the patent licensing is a separate question the standard does not settle.

TTF stores its content exactly. Saving it again changes nothing, so it can be opened, edited and re-saved as often as you like without accumulating damage — which is what makes it a working format rather than a delivery one.

FontForge, Glyphs and FontLab read 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.

Every current browser reads it.

That makes it a safe thing to put on a page or attach to a message without wondering what the other end has installed.

TTF is meant to be opened and changed. Keep the file in this format for as long as the work is going on, and export from it whenever a finished copy is needed.

Not pictures of letters. A TrueType font stores each character as an outline — a closed path described by points and quadratic curves — plus the instructions for putting them together into text. The outline is scalable, which is why the same file produces a crisp letter at 8 points and at 800.

Around the outlines sit tables of metadata: the character map, which says that the code point for A should draw this particular outline; the metrics, which say how wide each glyph is and how far apart lines should sit; the kerning pairs, which say that an A after a V should tuck in slightly. A font is a small database, and the letterforms are only part of it.

On Windows, double-click the file and choose Install, or drag it into the Fonts folder in Settings. Installing for all users needs administrator rights; installing for yourself does not, and is usually enough.

On macOS, double-click and Font Book offers to install it. On Linux, drop the file into a fonts directory in your home folder and refresh the cache.

One thing is the same everywhere: applications read the font list when they start. A font installed while your word processor is open will not appear in it until the program is restarted, and a great deal of time is lost to that every day.

A font is software, and it is licensed like software. A desktop licence covers installing it on a stated number of machines and using it to make things. It does not automatically cover putting the file on a web server, embedding it in an app, or handing it to a client — those are separate licences, priced separately, and the file will not stop you doing any of them.

This matters most in the direction people do not expect. Converting a licensed desktop font to a web format is technically trivial and is frequently a breach of the agreement that came with it. Free fonts are generally issued under the SIL Open Font License, which does permit it — and also requires that the font not be sold on its own and, if renamed, that reserved names are not reused. Read the licence file that came in the download; it is usually one page.

TrueType outlines carry instructions — a small stack-based program per glyph — telling the renderer how to distort the shape at small sizes so that stems land on whole pixels. That is hinting, and at the resolutions of the 1990s it was the difference between readable and blurry.

It matters much less now. High-density screens have enough pixels that a nudge is invisible, and macOS ignores hinting entirely. Fonts still carry it, badly hinted fonts still look worse on Windows at small sizes, and the whole apparatus is quietly becoming a historical curiosity.

They are the same container. OpenType was built on TrueType, and both are covered by the same ISO standard today, so the extension mostly tells you which kind of outline is inside: quadratic curves in a TTF, cubic PostScript curves in an OTF.

For a user, the practical difference is almost nil. Both install identically, both work in every application, and neither is higher quality by virtue of its extension. What can differ is what the designer put in — advanced typographic features such as true small capitals and stylistic alternates are more often present in an OTF, though nothing in the format prevents a TTF from having them.

Do not link the TTF directly. It works, and it is wasteful: WOFF2 is the same font compressed for transport, typically thirty to fifty per cent smaller, and every current browser reads it. Converting is the standard first step of putting a typeface on a site.

The second step is subsetting, which matters more than the format. A full font covering Latin, Cyrillic and Greek is several times the size of one covering only the characters an English page uses. Between subsetting and WOFF2 compression, a 300 KB desktop font routinely becomes a 25 KB web font — and the licence question above still applies before any of it.

Three causes cover nearly everything. The application was open when the font was installed, and needs restarting. The font is already installed in a different version, and the system silently kept the old one — uninstall first, then install again. Or the file was downloaded from the web and is blocked by the operating system, which on Windows shows as an install that appears to succeed and changes nothing.

A genuinely corrupt font file is rare and usually announces itself: the install dialog refuses it outright rather than half-working. If the file opens in a font previewer, it is intact.