1<p align="center"><img src="https://raw.githubusercontent.com/facebook/zstd/readme/doc/images/zstd_logo86.png" alt="Zstandard"></p> 2 3__Zstandard__, or `zstd` as short version, is a fast lossless compression algorithm, 4targeting real-time compression scenarios at zlib-level and better compression ratios. 5It's backed by a very fast entropy stage, provided by [Huff0 and FSE library](https://github.com/Cyan4973/FiniteStateEntropy). 6 7The project is provided as an open-source BSD-licensed **C** library, 8and a command line utility producing and decoding `.zst`, `.gz`, `.xz` and `.lz4` files. 9Should your project require another programming language, 10a list of known ports and bindings is provided on [Zstandard homepage](http://www.zstd.net/#other-languages). 11 12Development branch status : [![Build Status][travisDevBadge]][travisLink] [![Build status][AppveyorDevBadge]][AppveyorLink] [![Build status][CircleDevBadge]][CircleLink] 13 14[travisDevBadge]: https://travis-ci.org/facebook/zstd.svg?branch=dev "Continuous Integration test suite" 15[travisLink]: https://travis-ci.org/facebook/zstd 16[AppveyorDevBadge]: https://ci.appveyor.com/api/projects/status/xt38wbdxjk5mrbem/branch/dev?svg=true "Windows test suite" 17[AppveyorLink]: https://ci.appveyor.com/project/YannCollet/zstd-p0yf0 18[CircleDevBadge]: https://circleci.com/gh/facebook/zstd/tree/dev.svg?style=shield "Short test suite" 19[CircleLink]: https://circleci.com/gh/facebook/zstd 20 21### Benchmarks 22 23For reference, several fast compression algorithms were tested and compared 24on a server running Linux Debian (`Linux version 4.8.0-1-amd64`), 25with a Core i7-6700K CPU @ 4.0GHz, 26using [lzbench], an open-source in-memory benchmark by @inikep 27compiled with GCC 6.3.0, 28on the [Silesia compression corpus]. 29 30[lzbench]: https://github.com/inikep/lzbench 31[Silesia compression corpus]: http://sun.aei.polsl.pl/~sdeor/index.php?page=silesia 32 33| Compressor name | Ratio | Compression| Decompress.| 34| --------------- | ------| -----------| ---------- | 35| **zstd 1.1.3 -1** | 2.877 | 430 MB/s | 1110 MB/s | 36| zlib 1.2.8 -1 | 2.743 | 110 MB/s | 400 MB/s | 37| brotli 0.5.2 -0 | 2.708 | 400 MB/s | 430 MB/s | 38| quicklz 1.5.0 -1 | 2.238 | 550 MB/s | 710 MB/s | 39| lzo1x 2.09 -1 | 2.108 | 650 MB/s | 830 MB/s | 40| lz4 1.7.5 | 2.101 | 720 MB/s | 3600 MB/s | 41| snappy 1.1.3 | 2.091 | 500 MB/s | 1650 MB/s | 42| lzf 3.6 -1 | 2.077 | 400 MB/s | 860 MB/s | 43 44[zlib]:http://www.zlib.net/ 45[LZ4]: http://www.lz4.org/ 46 47Zstd can also offer stronger compression ratios at the cost of compression speed. 48Speed vs Compression trade-off is configurable by small increments. 49Decompression speed is preserved and remains roughly the same at all settings, 50a property shared by most LZ compression algorithms, such as [zlib] or lzma. 51 52The following tests were run 53on a server running Linux Debian (`Linux version 4.8.0-1-amd64`) 54with a Core i7-6700K CPU @ 4.0GHz, 55using [lzbench], an open-source in-memory benchmark by @inikep 56compiled with GCC 6.3.0, 57on the [Silesia compression corpus]. 58 59Compression Speed vs Ratio | Decompression Speed 60---------------------------|-------------------- 61 |  62 63A few other algorithms can produce higher compression ratios at slower speeds, falling outside of the graph. 64For a larger picture including slow modes, [click on this link](doc/images/DCspeed5.png). 65 66 67### The case for Small Data compression 68 69Previous charts provide results applicable to typical file and stream scenarios (several MB). Small data comes with different perspectives. 70 71The smaller the amount of data to compress, the more difficult it is to compress. This problem is common to all compression algorithms, and reason is, compression algorithms learn from past data how to compress future data. But at the beginning of a new data set, there is no "past" to build upon. 72 73To solve this situation, Zstd offers a __training mode__, which can be used to tune the algorithm for a selected type of data. 74Training Zstandard is achieved by providing it with a few samples (one file per sample). The result of this training is stored in a file called "dictionary", which must be loaded before compression and decompression. 75Using this dictionary, the compression ratio achievable on small data improves dramatically. 76 77The following example uses the `github-users` [sample set](https://github.com/facebook/zstd/releases/tag/v1.1.3), created from [github public API](https://developer.github.com/v3/users/#get-all-users). 78It consists of roughly 10K records weighing about 1KB each. 79 80Compression Ratio | Compression Speed | Decompression Speed 81------------------|-------------------|-------------------- 82 |  |  83 84 85These compression gains are achieved while simultaneously providing _faster_ compression and decompression speeds. 86 87Training works if there is some correlation in a family of small data samples. The more data-specific a dictionary is, the more efficient it is (there is no _universal dictionary_). 88Hence, deploying one dictionary per type of data will provide the greatest benefits. 89Dictionary gains are mostly effective in the first few KB. Then, the compression algorithm will gradually use previously decoded content to better compress the rest of the file. 90 91#### Dictionary compression How To: 92 931) Create the dictionary 94 95`zstd --train FullPathToTrainingSet/* -o dictionaryName` 96 972) Compress with dictionary 98 99`zstd -D dictionaryName FILE` 100 1013) Decompress with dictionary 102 103`zstd -D dictionaryName --decompress FILE.zst` 104 105 106### Build instructions 107 108#### Makefile 109 110If your system is compatible with standard `make` (or `gmake`), 111invoking `make` in root directory will generate `zstd` cli in root directory. 112 113Other available options include: 114- `make install` : create and install zstd cli, library and man pages 115- `make check` : create and run `zstd`, tests its behavior on local platform 116 117#### cmake 118 119A `cmake` project generator is provided within `build/cmake`. 120It can generate Makefiles or other build scripts 121to create `zstd` binary, and `libzstd` dynamic and static libraries. 122 123#### Meson 124 125A Meson project is provided within `contrib/meson`. 126 127#### Visual Studio (Windows) 128 129Going into `build` directory, you will find additional possibilities: 130- Projects for Visual Studio 2005, 2008 and 2010. 131 + VS2010 project is compatible with VS2012, VS2013 and VS2015. 132- Automated build scripts for Visual compiler by @KrzysFR , in `build/VS_scripts`, 133 which will build `zstd` cli and `libzstd` library without any need to open Visual Studio solution. 134 135 136### Status 137 138Zstandard is currently deployed within Facebook. It is used continuously to compress large amounts of data in multiple formats and use cases. 139Zstandard is considered safe for production environments. 140 141### License 142 143Zstandard is dual-licensed under [BSD](LICENSE) and [GPLv2](COPYING). 144 145### Contributing 146 147The "dev" branch is the one where all contributions are merged before reaching "master". 148If you plan to propose a patch, please commit into the "dev" branch, or its own feature branch. 149Direct commit to "master" are not permitted. 150For more information, please read [CONTRIBUTING](CONTRIBUTING.md). 151
