Zstd, short for Zstandard, is a fast lossless compression algorithm, targeting real-time compression scenarios at zlib-level compression ratio.

It is provided as a BSD-license package, hosted on Github.

Branch	Status
master
dev

For a taste of its performance, here are a few benchmark numbers from a number of compression codecs suitable for real-time. The test was completed on a Core i7-5600U @ 2.6 GHz, using fsbench 0.14.3, an open-source benchmark program by m^2.

Name	Ratio	C.speed	D.speed
		MB/s	MB/s
zstd 0.3	2.858	280	670
zlib 1.2.8 -1	2.730	70	300
QuickLZ 1.5.1b6	2.237	370	415
LZO 2.06	2.106	400	580
LZ4 r131	2.101	450	2100
Snappy 1.1.0	2.091	330	1100
LZF 3.6	2.077	200	560

Zstd can also offer stronger compression ratio at the cost of compression speed, but preserving its decompression speed. In the following test, a few compressors suitable for this scenario are selected (they offer very asymetric performance, useful when compression time has little importance). The test was completed on a Core i7-5600U @ 2.6 GHz, using benchmark 0.6.1, an open-source benchmark program by inikep.

Name	Ratio	C.speed	D.speed
		MB/s	MB/s
brotli -9	3.729	4	340
zstd 0.3 -9	3.447	30	640
zlib 1.2.8 -9	3.133	10	300
LZO 2.06 -999	2.790	1	560
LZ4 r131 -9	2.720	25	2100

Zstd compression speed is highly configurable, by small increment, to fit different situations. Its memory requirement can also be configured to fit into low-memory hardware configurations, or servers handling multiple connections/contexts in parallel.

Zstd entropy stage is provided by Huff0 and FSE, from Finite State Entrop library.

Zstd has not yet reached "stable" status. Specifically, it doesn't guarantee yet that its current compressed format will remain stable and supported in future versions. It may still change to adapt further optimizations still being investigated. That being said, the library is now pretty robust, able to withstand hazards situations, including invalid input. The library reliability has been tested using Fuzz Testing, with both internal tools and external ones. Therefore, it's now safe to test Zstandard even within production environments.

"Stable Format" is projected sometimes early 2016.

Branch Policy

The "dev" branch is the one where all contributions will be merged before reaching "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.