What is WOFF2? Web Open Font Format 2.0 Explained

How WOFF2 Works

WOFF2 is version 2 of the Web Open Font Format, and it does the same job as the original WOFF: it wraps an OpenType or TrueType font in a container built for the web. The glyph outlines, character maps, and layout tables inside are unchanged, and a browser reconstructs the original font from them. What sets WOFF2 apart is that it is far more aggressive about making that container small, which is the whole point of the revision.

The headline change is the compression engine. Where WOFF 1.0 compressed each table with general-purpose zlib, WOFF2 uses Brotli, a newer algorithm that consistently squeezes text-like data smaller. On top of that, WOFF2 applies a font-specific transform before compressing: it rearranges the glyf and loca tables into a form that exposes more redundancy for Brotli to exploit, understanding the structure of glyph outlines rather than treating them as an opaque blob. The two techniques together typically yield files roughly a quarter to a third smaller than the same font as WOFF 1.0.

WOFF2 also compresses the whole font as a single stream rather than table by table, which lets the compressor find patterns that span the entire file. This is more efficient but means a browser generally decodes the complete font before use rather than pulling out one table at a time. For a web font, where the whole file is needed to render text anyway, that is the right trade, and it contributes to the size win.

For the designer, none of this is visible. A WOFF2 font is referenced from a CSS @font-face rule with format("woff2"), downloaded like any other asset, and expanded back to a standard OpenType font in memory. Everything the underlying font supports, ligatures, kerning, multiple scripts, and variable-font axes, works exactly as it would from a desktop file, because the reconstructed font is byte-for-byte the original.

History and Standardization

WOFF2 grew out of work led by Google, which had strong reasons to shrink web fonts: every byte saved on a font speeds up page loads across an enormous number of sites. It built on the proven WOFF wrapper and paired it with Brotli, the compression algorithm Google was developing in the same period, adding the glyph-table transform to push the savings further.

The W3C standardized it as a formal Recommendation, the WOFF 2.0 File Format, giving it the same vendor-neutral footing as the original. Browser support followed quickly and is now effectively universal across current versions of Chrome, Firefox, Safari, and Edge. Because the retirement of Internet Explorer removed the last common browser that could not read WOFF2, it has become the default web font format for modern sites.

In current practice, WOFF2 is the primary format in a @font-face rule, often listed alone or with WOFF 1.0 as a single fallback for rare old browsers. The elaborate multi-format font stacks of the past, which juggled EOT, TTF, WOFF, and SVG fonts, have collapsed into essentially just WOFF2 plus at most one fallback. It represents the current end point of the web's long effort to deliver real typography efficiently.

WOFF2 Compared to WOFF and Raw Fonts

Against WOFF 1.0, WOFF2 is a straight improvement in size with no loss of capability: same fonts, same features, meaningfully fewer bytes thanks to Brotli and the glyph transform. The only reason to still serve WOFF 1.0 is compatibility with a shrinking set of older browsers, and even that need is largely gone. For any font a browser can render, WOFF2 is the smaller way to deliver it.

Against serving a raw .ttf or .otf, WOFF2 wins decisively on transfer size while decompressing to the very same font. A raw font can be gzipped by the server, but that does not match Brotli plus the font-aware transform, so WOFF2 is both smaller and simpler to deploy as a single self-contained file. Raw OpenType remains the master you convert from, not the file you ship to visitors.

One practical point worth remembering is that WOFF2, like every web font wrapper, is a delivery format, not an editing format. To modify a typeface, add glyphs, adjust spacing, or subset it, you work with the underlying OpenType source and generate a fresh WOFF2 at the end. Pairing WOFF2 with subsetting, shipping only the glyphs a page actually uses, produces the smallest possible web fonts, which is why it sits at the heart of modern performance-minded typography.