What is a .otf file?
OpenType Font · Font · Adobe / Microsoft · 1996
OTF is a modern font format that builds on TrueType with richer typographic features like ligatures, alternate glyphs and advanced spacing. It is a favourite of designers who want fine control over type.
What is a .otf file used for?
OpenType can use either TrueType or Adobe's CFF outlines and adds powerful features: ligatures, small caps, stylistic alternates and support for very large character sets.
It works across Windows, macOS and Linux just like TTF, so which one to choose usually comes down to the specific font's features.
For the web, OTF is again typically converted to WOFF2 for smaller, faster downloads.
How to open a .otf file
The .otf format opens in the following apps, grouped by operating system. If one app does not work, try another from the same list. For a step-by-step walkthrough, see how to open a .otf file.
Windows
- Windows Font Viewer
- FontForge
macOS
- Font Book
- FontForge
Linux
- Font viewer
- FontForge
Web
- Used via @font-face, prefer WOFF2
How to convert a .otf file
You can convert a .otf file to TTF, WOFF, WOFF2 using a conversion tool or the export menu of an app that opens it.
.otf file signature (magic bytes)
Programs recognise a .otf file by the bytes at the start of the file, not by its name. These are the signatures for OTF. For a full breakdown, see the OTF file signature page.
| Hex signature | Offset | Note |
|---|---|---|
| 4F 54 54 4F | 0 | 'OTTO' (CFF outlines) |
See the full magic-numbers reference for every format.
Frequently asked questions
What is a .otf file?
OTF is a modern font format that builds on TrueType with richer typographic features like ligatures, alternate glyphs and advanced spacing. It is a favourite of designers who want fine control over type.
Should I use OTF or TTF?
For everyday use they are interchangeable. Choose OTF when the font offers advanced typography like ligatures and alternates that you want to use.