Wuff

A lightweight, pure-Rust decoder for WOFF and WOFF2 web fonts.

Wuff takes a compressed WOFF or WOFF2 file and decodes it back into a plain OpenType/TrueType (sfnt) font that can be parsed by standard font tooling.

It is hand-ported from Google's woff2 C++ library and has been verified to produce byte-identical output to Google's woff2 library for every font in the google/fonts repository

Why Wuff?

• Pure Rust — no C/C++ toolchain or bindings required.
• Support both WOFF and WOFF2 formats
• Lightweight — minimal dependencies, with the compression backends behind optional features.
• Bring your own decompressor — use the bundled backends, or plug in your own Brotli/zlib implementation.

Encoding

Wuff currently only includes the decoder and does not yet have a port of the encoder. For encoding, consider:

• https://github.com/bearcove/woofwoof (Rust bindings to the C++ woff2 library)
• https://github.com/0x6b/ttf2woff2 (AI-assisted port of the C++ woff2 encoder to Rust)

Usage

Decode a WOFF2 file into an OpenType/TrueType font:

let woff2_bytes = std::fs::read("font.woff2")?;
let otf_bytes = wuff::decompress_woff2(&woff2_bytes)?;

Decode a WOFF (version 1) file:

let woff_bytes = std::fs::read("font.woff")?;
let otf_bytes = wuff::decompress_woff1(&woff_bytes)?;

Custom decompressors

If you'd rather not pull in the bundled compression crates (for example to share a Brotli implementation you already depend on), disable the default features and supply your own decompression closure:

use wuff::decompress_woff2_with_custom_brotli;

let otf_bytes = decompress_woff2_with_custom_brotli(&woff2_bytes, &mut |input, hint| {
    // Decompress `input`, optionally using `hint` as a size hint for the output buffer.
    my_brotli_decompress(input, hint)
})?;

A matching decompress_woff1_with_custom_z is available for WOFF1.

Conformance testing

The conformance crate is a test harness which verifies that three decoders produce byte-identical output for every font it tests:

1. Google's C++ woff2 reference decoder (the woff2_decompress binary)
2. The wuff Rust decoder (this crate)
3. The wuff-capi C++ wrapper around the wuff decoder

Requirements: a C++ toolchain, plus cmake and brotli to build the C++ woff2 tools.

Its inputs are:

• The WOFF2 files from the css/WOFF2 section of the web-platform-tests committed to this repository under conformance/fonts/wpt/. This test suite contains deliberately invalid WOFF2 files, so consistent rejection by all three decoders is considered a test pass.
• Every ttf/otf/ttc font in the google/fonts repository, encoded to WOFF2 with the C++ reference encoder (woff2_compress).

Run it with:

cargo run -rp conformance
cargo run -rp conformance --refresh-fonts  # re-download google/fonts and rebuild the cache

The first run downloads the google/fonts repository (~1.5GB) and encodes every font at maximum Brotli quality, which takes a while. The encoded WOFF2 files (~820MB) are cached in .data/encoded. Use --refresh-fonts to a force a cache refresh.

Repository layout

This repository contains both the published crate and the reference material used to develop it:

• wuff/ - the published crate: an idiomatic Rust rewrite of the decoder.
• wuff-capi/ - a C API for the wuff decoder, usable as a drop-in replacement for the woff2 C++ library's decoding API.
• conformance/ - the conformance test harness described above.
• woff2/ - a copy of Google's woff2 C++ library, used as the reference implementation.

License

Licensed under the MIT License.