.woff File Extension

What kind of file is a .woff?

A .woff file is a Web Open Font Format 1.0 resource. It packages an existing table-based sfnt font, usually TrueType or OpenType, for delivery to a web browser. It uses the registered font/woff MIME type.¹²

WOFF may compress individual font tables with zlib, but it does not define new glyph outlines or typographic features. A conforming decoder restores font data that renders identically to the well-formed source font.¹

The first four bytes are 77 4F 46 46, which spells wOFF in ASCII. The 44-byte header also records the underlying font flavor, file length, table count, restored size, and offsets to optional metadata and private data. A reliable tool validates the header and table directory instead of trusting the suffix alone.¹

How do I open a .woff on my computer?

WOFF is meant to be loaded from a web page through CSS @font-face, not installed as an ordinary desktop font.¹

• In Chrome, Edge, Firefox, Opera, or Safari, reference the file from a page's CSS. Serve it with Content-Type: font/woff.³
• On Windows, macOS, or Linux, use a font tool such as FontForge or fontTools to validate or unpack it for inspection.
• For a quick visual check, build a small HTML specimen that exercises the weights, styles, languages, and OpenType features your site needs.

Cross-origin font requests need appropriate access-control headers. If a page offers both formats, list .woff2 first and .woff second as the older-browser fallback.

Poly support for .woff

Poly stores, syncs, shares, versions, and downloads WOFF fonts, and you can find them by filename and ordinary file properties. Poly does not currently unpack the container, render a font specimen, index family names or character coverage, or expose glyphs and font tables to the agent.

Download the file and inspect it with a trusted font tool or test page when you need to verify glyphs, variation axes, layout features, metadata, or licensing details.

History of .woff

WOFF began as a collaboration among browser and type developers. Jonathan Kew, Tal Leming, and Erik van Blokland authored the specification, which the W3C WebFonts Working Group developed into a Recommendation on December 13, 2012.¹⁴

The original media type was application/font-woff. RFC 8081 established the dedicated font top-level type in 2017 and deprecated that label in favor of font/woff.²

Working with .woff and alternatives

WOFF2 adds font-aware preprocessing and Brotli compression, so it is normally the better web-delivery choice. Keep the original TTF or OTF master when converting, and verify that subsetting has not removed required characters or features.⁵

Treat unfamiliar fonts as untrusted input. Font parsers handle complex binary structures, and hinting instructions can behave like executable code. Keep browsers and font tools updated. Also check the license before converting, embedding, or redistributing a font. A desktop license does not necessarily grant web use.¹²