brotli-wasm

Part of HTTP Toolkit: powerful tools for building, testing & debugging HTTP(S)

A reliable compressor and decompressor for Brotli, supporting node & browsers via wasm

Brotli is available in modern Node (12+) but not older Node or browsers. With this package, you can immediately use it everywhere.

This package contains a tiny wrapper around the compress & decompress API of the Rust Brotli crate, compiled to wasm with just enough setup to make it easily usable from JavaScript.

This is battle-tested, in production use in both node & browsers as part of HTTP Toolkit, and includes automated build with node & browser tests to make sure.

Getting started

npm install brotli-wasm

You should be able to import this directly into Node, as normal, or into a browser using any bundler that supports ES modules & webassembly (e.g. Webpack v4 or v5).

The browser build supports both sync (v4 or v5 syncWebAssembly mode) and async (v5 asyncWebAssembly) builds. When imported in a browser build the module always exports a promise, not a fixed value, as this is a requirement for synchronous builds, and you will need to await this after import.

In both builds, the module exposes two methods:

• compress(Buffer, [options]) - compresses a buffer using Brotli, returning the compressed buffer. An optional options object can be provided. The only currently supported option is quality: a number between 1 and 11.
• decompress(Buffer) - decompresses a buffer using Brotli, returning the original raw data.

In node.js:

const * as brotli = require('brotli-wasm');

const compressedData = brotli.compress(Buffer.from('some input'));
const depressedData = brotli.decompress(compressedData);

console.log(Buffer.from(decompressedData).toString('utf8')); // Prints 'some input'

In browsers:

import * as brotliPromise from 'brotli-wasm';

const brotli = await brotliPromise; // Import is async in browsers due to wasm requirements!

const compressedData = brotli.compress(Buffer.from('some input'));
const depressedData = brotli.decompress(compressedData);

console.log(Buffer.from(decompressedData).toString('utf8')); // Prints 'some input'

You'll need a browser Buffer polyfill for the above, or you can do the same using TextEncoder/Decoder instead if you prefer.

If you want to support node & browsers with the same code, you can use the latter await form here everywhere (since awaiting the fixed value in node just returns the value as-is).

Alternatives

There's a few other packages that do similar things, but I found they were all unusable and/or unmaintained:

• brotli-dec-wasm - decompressor only, compiled from Rust just like this package, actively maintained, but no compressor available (by design). If you only need decompression, this package is a good choice.
• Brotli.js - hand-written JS decompressor that seems to work OK for most cases, but it crashes for some edge cases and the emscripten build of the compressor doesn't work in browsers at all. Last updated in 2017.
• wasm-brotli - Compiled from Rust like this package, includes decompressor & compressor, but requires a custom async wrapper for Webpack v4 usage and isn't usable at all in Webpack v5. Last updated in 2019.