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Node.js bindings for Zopfli compressing 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

or if you want zopfli binary globally

npm install -g node-zopfli

Binary (from command line)

To gzip a file

zopfli file.txt

To compress a png file

zopflipng file.png out.png

Usage examples

Stream (async):

var zopfli = require('node-zopfli');

Instead of zopfli.createGzip, you can also use

new Zopfli('gzip', options);

Buffer (async):

var zopfli = require('node-zopfli');
var 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):

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


compress(input, format, [options, callback])

input is the input buffer

format can be one of deflate, zlib and gzip

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

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


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


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
npm install


mocha is used for tests, you can run them with:

npm test


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







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