A Zopflli binding in universal JavaScript, built into WebAssembly

Usage no npm install needed!

<script type="module">
  import gfxZopfli from 'https://cdn.skypack.dev/@gfx/zopfli';


Universal Zopfli npm version Build Status

google/zopfli is a compression library to perform gzip, deflate or zlib compression.

This library is a JavaScript binding to zopfli with WebAssembly. This is slower than native extensions for zopfli, but because wasm is a portable binary format, its installation is much easier than native extensions.


# for npm users:
npm install "@gfx/zopfli"

# for yarnpkg users
yarnpkg add "@gfx/zopfli"


In TypeScript:

import { gzip, zlib, deflate } from "@gfx/zopfli";

const input: string;
gzip(input, { numiterations: 15 }, (err, output) => {
    // output is compressed in gzip

Note that the gzip method is compatible with node-zopfli.


Exported as ZopfliOptions and its default is:

const defaultOptions: ZopfliOptions = {
    verbose: false,
    verbose_more: false,
    numiterations: 15,
    blocksplitting: true,
    blocksplittingmax: 15,

Using Zopfli with promises for async/await

There are "async"-suffixed versions that return promises:

// These functions return `Promise<T>` for async/await.
import { gzipAsync, zlibAsync, deflateAsync } from "@gfx/zopfli";

Using Zopfli in Webpack CompressionPlugin

You can give the zopfli.gzip function to CompressionPlugin:

// in webpack.config.js

const CompressionPlugin = require('compression-webpack-plugin');
const { gzip } = require('@gfx/zopfli');

module.exports = {
  plugins: [
    new CompressionPlugin({
      algorithm: gzip,






make benchmark-with-optimization

As of emscripten 1.38.37 with LLVM backend + NodeJS v10.16.0 + macOS 10.14.4, the result is as follows:

## payload size: 1
universal-zopfli x 162 ops/sec ±3.82% (80 runs sampled)
node-zopfli x 185 ops/sec ±3.37% (77 runs sampled)
Fastest is node-zopfli
## payload size: 1024
universal-zopfli x 2.04 ops/sec ±3.48% (14 runs sampled)
node-zopfli x 5.02 ops/sec ±1.03% (28 runs sampled)
Fastest is node-zopfli
## payload size: 1038336
universal-zopfli x 0.33 ops/sec ±6.77% (6 runs sampled)
node-zopfli x 0.32 ops/sec ±17.77% (6 runs sampled)
Fastest is universal-zopfli,node-zopfli

That is, the performance of universal-zopfli is about 50%-75% of native binding node-zopfli with 1KiB-1MiB payload.

See Also


Copyright 2017, FUJI Goro (gfx).

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at


Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.

And it links to google/zopfli statically, which is also licensed by Google under Apache 2.0 License.