What is a .otf file?
A .otf file is an openType font. Its registered MIME type is font/otf, which places it in the font family of formats.
Technically it is a specialised form of font/ttf (the .ttf format), so tools that understand that format can often read at least part of it.
OTF is a binary format: the contents are not readable text, so opening it in a text editor shows scrambled characters.
Files of this type usually begin with the bytes 4F 54 54 4F. That signature is how programs recognise the format even when the extension is wrong or missing.
OTF file format details
| Extension | .otf |
|---|---|
| Format | OpenType font |
| MIME type | font/otf, application/vnd.oasis.opendocument.formula-template, application/x-font-otf |
| Category | Font |
| Text or binary | Binary |
| Based on | font/ttf |
| File signature | 4F 54 54 4F |
| Registered with IANA | Yes |
| Other extensions | None |
How to open OTF files
| Windows | Double-click the font file to preview it, then choose Install. |
|---|---|
| Mac | Double-click the font to open Font Book, then click Install. |
| iPhone and iPad | Fonts are installed through apps that provide them, or through a configuration profile. |
| Android | System fonts cannot be changed on most phones; apps that support custom fonts let you pick the file. |
Convert OTF files
TapToConvert converts OTF files in your browser, without uploading them. Open the OTF converter, or go straight to a conversion:
OTF file FAQ
What is a .otf file?
A .otf file is an openType font, with the MIME type font/otf.
How do I open a .otf file?
With the program that created it. The viewer on this page shows what is inside without installing anything.
Is a .otf file safe to open?
OTF files hold data rather than programs, but any file from an unknown source can be crafted to exploit the software that opens it. Keep that software up to date. The viewer on this page only reads the bytes and never runs anything.
What is the MIME type of .otf?
font/otf, and it is also seen as application/vnd.oasis.opendocument.formula-template or application/x-font-otf. Web servers send this type so browsers know how to handle the file.
Is OTF a text or binary format?
Binary. Its contents are not readable as text.
File type facts come from the IANA media type registry, the mime-db project and the freedesktop.org shared MIME database.