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This library will only receive sporadic updates and new features are out of question.


NODEJS LEGACY (<12) (no module support)

This is a fork of node-zopfli, created to fix some security issues which have since been resolved.

Since node-zopfli is maintained again, switching back to it is advised.

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Node.js bindings for Zopfli compression library. Compress gzip files 5% better compared to gzip.

It is considerably slower than gzip (~100x) so you may want to use it only for static content and cached resources.

Prerequisites for building


npm install node-zopfli-es

or if you want zopfli binary globally

npm install -g node-zopfli-es

Usage examples

Binary (from command line)

To gzip a file

zopfli file.txt

To compress a png file

zopflipng file.png out.png

Stream (async):

const zopfli = require('node-zopfli-es')

Instead of zopfli.createGzip, you can also use

new Zopfli('gzip', options)

Buffer (async):

const zopfli = require('node-zopfli-es')
const input = new Buffer('I want to be compressed')
zopfli.deflate(input, options, function (err, deflated) {})
zopfli.zlib(input, options, function (err, zlibed) {})
zopfli.gzip(input, options, function (err, gziped) {})

Buffer (sync):

const zopfli = require('node-zopfli-es')
const input = new Buffer('I want to be compressed')
const deflated = zopfli.deflateSync(input, options)
const zlibed = zopfli.zlibSync(input, options)
const gziped = zopfli.gzipSync(input, options)


compress(input, [format = 'deflate', options = {}, callback])

input is the input buffer (or string)

format can be one of deflate, zlib and gzip, deflate is the default if omitted

callback, if present, gets two arguments (err, buffer) where err is an error object, if any, and buffer is the compressed data.

If format is a function and callback is not, format is set to deflate and callback gets set If options is a function and callback is not, options are set to {} and callback gets set

If no callback is provided, it returns an A+ Promise.


deflate, zlib and gzip methods are aliases on compress without format argument.

deflate(input, [options = {}, callback])

zlib(input, [options = {}, callback])

gzip(input, [options = {}, callback])


Here are the options with defaults values you can pass to zopfli:

  verbose: false,
  verbose_more: false,
  numiterations: 15,
  blocksplitting: true,
  blocksplittinglast: false,
  blocksplittingmax: 15,

Maximum amount of times to rerun forward and backward pass to optimize LZ77 compression cost. Good values: 10, 15 for small files, 5 for files over several MB in size or it will be too slow.


If true, splits the data in multiple deflate blocks with optimal choice for the block boundaries. Block splitting gives better compression.


If true, chooses the optimal block split points only after doing the iterative LZ77 compression. If false, chooses the block split points first, then does iterative LZ77 on each individual block. Depending on the file, either first or last gives the best compression.


Maximum amount of blocks to split into (0 for unlimited, but this can give extreme results that hurt compression on some files).

Build from sources

git clone --recursive
cd node-zopfli-es
npm install


@magic/test is used, you can run it with:

npm test

The npm test command also runs nyc to create coverage reports.

Fast testing without coverage:

npm start


@magic/test also includes prettier:

# equal to: prettier --write
npm run format

# equal to: prettier --list-different
npm run format:check


Someone pushed the type definitions to DefinitelyTyped:

npm install @types/node-zopfli-es

Typescript definitions


Node bindings for Zopfli Compression Algorithm (zlib, gzip, deflate compatible)







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