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Extremely Fast Compression algorithm
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LZ4 - Extremely fast compression

LZ4 is lossless compression algorithm, providing compression speed > 500 MB/s per core, scalable with multi-cores CPU. It features an extremely fast decoder, with speed in multiple GB/s per core, typically reaching RAM speed limits on multi-core systems.

Speed can be tuned dynamically, selecting an "acceleration" factor which trades compression ratio for faster speed. On the other end, a high compression derivative, LZ4_HC, is also provided, trading CPU time for improved compression ratio. All versions feature the same decompression speed.

LZ4 is also compatible with dictionary compression, and can ingest any input file as dictionary, including those created by Zstandard Dictionary Builder. (note: only the final 64KB are used).

LZ4 library is provided as open-source software using BSD 2-Clause license.

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Branch Policy:

  • The "master" branch is considered stable, at all times.
  • The "dev" branch is the one where all contributions must be merged before being promoted to master.
    • If you plan to propose a patch, please commit into the "dev" branch, or its own feature branch. Direct commit to "master" are not permitted.


The benchmark uses lzbench, from @inikep compiled with GCC v7.3.0 on Linux 64-bits (Debian 4.15.17-1). The reference system uses a Core i7-6700K CPU @ 4.0GHz. Benchmark evaluates the compression of reference Silesia Corpus in single-thread mode.

Compressor Ratio Compression Decompression
memcpy 1.000 13100 MB/s 13100 MB/s
LZ4 default (v1.8.2) 2.101 730 MB/s 3900 MB/s
LZO 2.09 2.108 630 MB/s 800 MB/s
QuickLZ 1.5.0 2.238 530 MB/s 720 MB/s
Snappy 1.1.4 2.091 525 MB/s 1750 MB/s
Zstandard 1.3.4 -1 2.877 470 MB/s 1380 MB/s
LZF v3.6 2.073 380 MB/s 840 MB/s
zlib deflate 1.2.11 -1 2.730 100 MB/s 380 MB/s
LZ4 HC -9 (v1.8.2) 2.721 40 MB/s 3920 MB/s
zlib deflate 1.2.11 -6 3.099 34 MB/s 410 MB/s

LZ4 is also compatible and optimized for x32 mode, for which it provides additional speed performance.


make install     # this command may require root permissions

LZ4's Makefile supports standard Makefile conventions, including staged installs, redirection, or command redefinition. It is compatible with parallel builds (-j#).


The raw LZ4 block compression format is detailed within lz4_Block_format.

Arbitrarily long files or data streams are compressed using multiple blocks, for streaming requirements. These blocks are organized into a frame, defined into lz4_Frame_format. Interoperable versions of LZ4 must also respect the frame format.

Other source versions

Beyond the C reference source, many contributors have created versions of lz4 in multiple languages (Java, C#, Python, Perl, Ruby, etc.). A list of known source ports is maintained on the LZ4 Homepage.

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