Brotli decompressor for browsers and web workers with WASM, but still having a small size (about 300KB)

brotli, brotli-decompressor, wasm, rust
npm install brotli-dec-wasm@1.3.2



Brotli decompressor for browsers and web workers with WASM, but still having a small size (about 300KB)

If you are looking for a compressor, see Alternatives


Quick start

// One-shot decompressing
const brotli = await import('brotli-dec-wasm')
const output = brotli.brotliDec(input)

// Streaming decompressing
const brotli = await import('brotli-dec-wasm')
const stream = new brotli.BrotliDecStream()
// Set max output buffer size as 1024
const output1 = stream.dec(input1, 1024)
const result = stream.result()
// If result = NeedsMoreInput = 1, put more input into the stream to get next output
if (result == brotli.BrotliDecStreamResult.NeedsMoreInput) {
  const output2 = stream.dec(input2, 1024)
// If result = NeedsMoreOutput = 2, slice the input and take another output buffer out
if (result == brotli.BrotliDecStreamResult.NeedsMoreOutput) {
  const input1r = input1.slice(steam.lastInputOffset())
  const output2 = stream.dec(input1r, 1024)
// If result = ResultSuccess = 3, decompressing succeeded and finished. No more input is required.
if (result == brotli.BrotliDecStreamResult.ResultSuccess) {
// If result < 0, an error occurs. You may refer BrotliDecStreamErrCode to lookup the error code.
if (result < 0) {
  console.error('Brotli decompressing failed')


Broken in webpack 5

BREAKING CHANGE: Since webpack 5 WebAssembly is not enabled by default and flagged as experimental feature. You need to enable one of the WebAssembly experiments via 'experiments.asyncWebAssembly: true' (based on async modules) or 'experiments.syncWebAssembly: true' (like webpack 4, deprecated).

Set experiments.syncWebAssembly: true for old code. As for experiments.asyncWebAssembly: true, an example is available as a test in tests/webpack5.


The code is quite simple, which is just a wrapper of brotli-decompressor crate (other than brotli crate, though brotli depends on brotli-decompressor)

Build configuration such as opt-level = "s", are fine-tuned with manual tests, to make the bundle as small as possible


The package is at least used by myself in my blog mylmoe, which provides a page to (de)compress Brotli online


  • brotli-wasm: A reliable compressor and decompressor for Brotli, supporting node & browsers via wasm. If you need a compressor, use it. Actively maintained by an organization.

More alternatives are available in brotli-wasm Alternatives section

One surprising thing is, in js folder of the offical google/brotli repository, there is a pure JavaScript decompressor implementation, which is even a little smaller than this package in size. However, it is not published on NPM. I can not imagine the reason and since that, I do not suggest you to use it.


SPDX-License-Identifier: MIT

Unless otherwise explicitly stated