OTF (OpenType Font)
The font format that merged two competing worlds into one file.
| Full name | OpenType Font |
| Extension | .otf |
| MIME type | font/otf |
| Developer | Microsoft and Adobe Systems |
| Released | 1996 (announced); 1997 (specification 1.0) |
| Type | Font container |
| Glyph outlines | CFF (PostScript) or TrueType |
| Latest specification | OpenType 1.9 (2021) |
What is a OTF file?
OTF is the file extension for OpenType fonts that store glyph outlines in PostScript (CFF) format. OpenType is a joint font standard created by Microsoft and Adobe Systems, first announced in 1996. It is now maintained by the World Wide Web Consortium (W3C) through the MPEG group and is the dominant font format in professional typography.
An OTF file packages everything a font needs into a single file: glyph outlines, spacing metrics, kerning tables, and advanced typographic features. The format can hold PostScript CFF outlines (the classic OTF) or TrueType outlines (which carry the TTF extension instead). OTF fonts support Unicode, meaning a single file can cover tens of thousands of characters across many writing systems. Advanced layout features like ligatures, small caps, old-style numerals, and contextual alternates are all stored inside the same file.
History
Microsoft began developing TrueType Open in 1994 after negotiations with Apple over GX Typography technology broke down. Adobe joined the effort in 1996, contributing PostScript Type 1 outline technology, and the two companies jointly announced OpenType that year. The OpenType 1.0 specification shipped in 1997, and the first commercial OpenType fonts reached the market around 2000.
How it works
An OTF file is a collection of binary tables stored in the SFNT container, a format originally developed for TrueType. Each table has a four-character tag (like 'cmap', 'GPOS', 'GSUB') and holds a specific piece of font data. The 'CFF ' table stores PostScript glyph outlines in Compact Font Format, which is what distinguishes a true OTF from a TrueType-based font. Layout tables like GSUB (glyph substitution) and GPOS (glyph positioning) power the advanced typographic features that designers rely on.
What it is used for
- Professional print and publishing workflows where advanced typographic control is required
- Web typography via @font-face, supported in all modern browsers
- Graphic design software such as Adobe Illustrator, InDesign, and Affinity Publisher
- Operating system-level text rendering on Windows, macOS, and Linux
How to open it
OTF fonts install directly on Windows, macOS, and most Linux distributions by double-clicking the file and choosing Install. Once installed, any application that uses system fonts can access them, including word processors, design tools, and browsers.
Pros and cons
Strengths
- Supports over 65,000 glyphs per font, covering multiple languages and symbols in one file
- Advanced typographic features (ligatures, swashes, small caps) are built into the file
- Cross-platform: the same OTF file works on Windows, macOS, and Linux without modification
- PostScript CFF outlines render crisply at high resolutions and in print workflows
Trade-offs
- CFF outlines can render less sharply than TrueType at small screen sizes without good hinting
- Advanced OpenType features require application support; not all programs expose them
- File size grows quickly when a font includes many glyphs or language sets
- Editing OTF files requires specialized font editors such as FontLab or Glyphs
Convert OTF files
Free, in your browser, no signup. Start at the OTF converter, or jump straight to a popular conversion below.
Curious how fast and how small? See our measured conversion benchmarks.
OTF FAQ
What is the difference between OTF and TTF?
Both are OpenType fonts, but OTF uses PostScript CFF outlines while TTF uses TrueType outlines. OTF is preferred in professional print work; TTF historically hinted better at small screen sizes. For most everyday uses the difference is invisible.
Can I use OTF fonts on websites?
Yes. All modern browsers support OTF via the CSS @font-face rule. For best performance, convert OTF to WOFF2 first, since WOFF2 is compressed and loads faster over the web.
Who created the OpenType format?
Microsoft and Adobe Systems created OpenType together. Microsoft had been developing TrueType Open since 1994, and Adobe joined in 1996 to add PostScript outline support. The OpenType 1.0 specification was published in 1997.
How do I install an OTF font on my computer?
On Windows, right-click the OTF file and choose Install or Install for all users. On macOS, double-click the file and click Install Font. On most Linux systems, copy the file to ~/.local/share/fonts and run fc-cache -f.