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LZ-based compression algorithm for JavaScript


The file layout has changed in version 2, this is now a joint commonjs / esmodule project so modern build tools should be happy with it, but if importing a file directly (such as in a direct javascript project) it is important to use the correct one.


The "old style" minified AMD file is available as dist/index.umd.js via various CDNs or package managers.

Install via npm

$ npm install -g lz-string
$ lz-string input.txt > output.txt

Home page

Home page for this program with examples, documentation and a live demo:

Command line

If installed globally there is a command line tool available, and a test suite that can use it to show things are working properly. If other langauges build a command line tool that supports the same arguments then the test suite can be run against them too.

$ lz-string -h
Usage: cli [options] [input-file]

Use lz-string to compress or decompress a file

  input-file                  file to process, if no file then read from stdin

  -V, --version               output the version number
  -d, --decompress            if unset then this will compress
  -e, --encoder <type>        character encoding to use (choices: "base64", "encodeduri", "raw", "uint8array", "utf16", default: "raw")
  -v, --verify                verify before returning (default: true)
  -b, --binary <file>         lz-string binary to use (default: "../dist/index.js")
  -l, --legacy                use legacy mode where uint8array decompression must be an even length
  -o, --output <output-file>  output file, otherwise write to stdout
  -q, --quiet                 don't print any error messages
  -h, --help                  display help for command

Other languages

This lib has numerous ports to other languages, for server side processing, mostly. Here they are:


These are all developed separately, so if you are using two versions to transfer data (such as a client and server version) it is important to check that they are compatible and have identical behaviours on the data!


Version 1.3.8 of this package had a slight change in the encoding which might impact compatibility.