WOFF File Format (.woff)
A WOFF file wraps a TrueType or OpenType font in a compressed container built specifically for loading with @font-face on the web.
WOFF at a glance#
| Full name | Web Open Font Format |
|---|---|
| File extension | .woff |
| Category | Fonts |
| Developer | Jonathan Kew, Tal Leming, and Erik van Blokland |
| First released | 2009 |
| MIME types | font/woffapplication/font-woff |
| Compression | Lossless |
| Specification | WOFF File Format 1.0 |
| FileFlip support | FileFlip reads and writes this format |
What a .woff file can hold#
These are the things a WOFF file either supports or does not, and they are what decides whether a conversion keeps everything or quietly drops something.
| Embedded metadata | Yes |
|---|
Strengths and limitations of WOFF#
What WOFF does well
- Compresses the wrapped TrueType or OpenType data, typically shrinking it by more than 40 percent
- Supported by every browser still in use, including versions that predate WOFF2
- Carries metadata and license text in the container alongside the font data
Where WOFF falls short
- WOFF2's Brotli compression beats WOFF's zlib compression on the same font by a further margin
- Only useful for web embedding; desktop operating systems don't install WOFF files as system fonts
- Decompressing it costs a step that an uncompressed TTF never needs, even though the download is smaller
Serve WOFF when a site's browser support has to reach back further than WOFF2 covers, or as the fallback source in a @font-face src list.
Convert WOFF to WOFF2 as the primary web font and keep WOFF only as a fallback, since WOFF2 is smaller for the same font on every modern browser.
How to open a .woff file#
A .woff file opens in the programs below, grouped by the platform you are on. If you would rather not install anything, FileFlip converts WOFF into a format your machine already opens, and it does it in the browser tab rather than on a server.
| Platform | Programs that open it |
|---|---|
| Windows | FontForge |
| macOS | FontForge |
| Linux | FontForge |
| Web | FileFlip |
WOFF questions people ask#
Why is WOFF smaller than a plain TTF file?
WOFF wraps the same TrueType or OpenType glyph data inside a zlib-compressed container, which typically shrinks the file by more than 40 percent. Decompression happens once when the browser loads the font, so the smaller download comes at essentially no runtime cost.
Should I use WOFF or WOFF2 on my website?
WOFF2 compresses better than WOFF because it uses Brotli instead of zlib, and every browser still receiving updates supports it, so WOFF2 should be the primary format in a @font-face declaration. WOFF is worth keeping only as a fallback source for the handful of older browsers that never picked up WOFF2.
Can I install a WOFF file as a font on my computer?
Not directly. WOFF is a delivery format for the web, and operating systems expect an installable font like TTF or OTF rather than a WOFF container, so a WOFF file needs converting to TTF or OTF before Font Book or Windows Font Viewer will install it.
Converting WOFF files#
Convert WOFF to another format
Convert another format to WOFF
Every conversion runs inside your browser. The file is read from your disk, the work happens on your own machine, and nothing is uploaded. How FileFlip works names the engine behind each family and how to verify that for yourself.