OTF file format: what it is and how to use it

OpenType is the font format that ended the format wars: PostScript outlines, cross-platform, with typographic features like ligatures and alternates. Learn when to use it and what to choose instead.

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What is a OTF file?

An .otf file is a font in OpenType, the 1996 Microsoft-Adobe joint spec that merged TrueType's structure with PostScript (CFF) outlines: one cross-platform file holding glyph curves plus layout features such as ligatures, small caps, alternates, kerning classes and language-specific shaping. It is the professional standard for desktop typography.

When should you use OTF?

  • Design and print work: PostScript outlines and the full feature set.
  • System-wide installs: works identically on Windows, macOS and Linux.
  • Advanced typography: ligatures, alternates, stylistic sets and complex-script shaping.

When is another format a better fit?

For the web, WOFF2 is the delivery format, the same font compressed for bandwidth. For pixel-hinted rendering on low-DPI screens, TTF's TrueType outlines hint better. For variable fonts both .otf and .ttf carry them, but WOFF2 is still the web answer.

The short version: OTF is the professional desktop font. Install it for design work, and convert to WOFF2 for the website.

How to open a OTF file

On Windows

Double-click the file, or open it with Windows Font Viewer.

On macOS

macOS Font Book opens OTF files on macOS.

Convert instead

Turn OTF files into another format, right in the browser.

Also opens in

  • Windows Font Viewer
  • macOS Font Book
  • FontForge
  • Glyphs

Convert OTF files

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OTF technical details

Full name
OpenType font
Extensions
.otf
MIME type
font/otf
Magic bytes
4F 54 54 4F (OTTO)
Compression
None (uncompressed)
Developer
Adobe & Microsoft
Specification
learn.microsoft.com

OTF questions, answered

How do I open an .otf file?

Double-click to preview on any OS; install it to use in apps. Font editors (FontForge, Glyphs, FontLab) edit it. dexrr displays and converts otf files in your browser.

Can I convert OTF files online?

Yes, dexrr converts otf locally in your browser: OTF to WOFF2 for web use, OTF to TTF for TrueType outlines or OTF to WOFF for older web stacks.

Is OTF better than TTF?

For design features and print, generally yes: PostScript outlines and richer typography. For screen hinting, TTF's TrueType outlines can render crisper on low-DPI displays.

What is the difference between OTF and WOFF2?

WOFF2 is the web-delivery wrapper: the same font data compressed ~30% smaller, meant for @font-face. OTF is the desktop install form.

Is the OTF format outdated?

No, OpenType is the current desktop font standard and the basis of variable fonts.