What is WOFF (Web Open Font Format)?

What to know about this font format for the web

Web Open Font Format (WOFF) is a file format for web fonts developed by Mozilla. A WOFF file can contain compressed TTF and OTF files as well as licensing information and other metadata. Here's what you need to know about WOFF.

Information in this article applies to WOFF and WOFF2 files.

What Is a WOFF File?

Similar to ZIP files, WOFF files act as containers for other files, specifically TrueType Font (TTF) and OpenType Font (OTF) files. These types of files give web designers the ability to use fonts outside of the standard characters found on most computers.

WOFF has been superseded by the WOFF2 format. WOFF2 offers even better compression algorithms, which reduces the original file size by an additional 30 percent. Therefore, WOFF2 files take up less bandwidth and load even faster. WOFF files have the extension .woff, while WOFF2 files have the extension .woff2.

How Do WOFF Files Work?

Virtually all web pages use Cascading Style Sheets (CSS) to define the layout of HTML and other elements on your screen. For example, developers can use CCS to change web fonts by referencing fonts that are already installed on the user's computer. However, if your PC or browser doesn't support a font, it will appear as a different font or not load at all depending on how the page's font stack is set up.

To avoid this problem, custom fonts can be stored in a WOFF file, which is saved on a server with all of the other web page elements. The designer can then use the @font-face CSS property to reference the WOFF file and render the font in the browser.

Google Chrome, Firefox, Microsoft Edge, Opera, and Safari all support the WOFF format, but you may need to update your web browser to the latest version.

Benefits of WOFF

In addition to broadening the types of fonts that are available to web developers, using WOFF files has several advantages. For example:

  • Compression: Since WOFF files are compressed, they load faster than other font file types.
  • HTML and CSS Support: Unlike image files, WOFF files can be stylized with HTML and CSS.
  • SEO: WOFF fonts are better for search engine optimization (SEO) than images of text.
  • Optimized rendering: WOFF files include typographical information including contextual forms and old-style figures, allowing for optimal rendering on all devices.
  • Website accessibility: WOFF files make sites more accessible since text can be read aloud and images of text cannot.
  • Embedding: WOFF fonts help with internationalization by allowing you to embed fonts with characters from other languages.

Create Your Own WOFF Fonts

Font editors like FontForge allow you to design your own font sets and export them as WOFF files. You can also convert WOFF to TTF or OTF files using FontForge. If you have a different font editor you like that only supports TTF or OTF, you can use the sfnt2woff tool to convert the fonts to WOFF files.

Open Font Library and Font Squirrel have hundreds of fonts in the WOFF format that are free for commercial and non-commercial use.