Extremely fast non-cryptographic hash algorithm

Clone this repo:
  1. 7fc5ce8 minor cleaning by Yann Collet · 6 years ago dev
  2. f6dcd54 Merge pull request #98 from wuxb45/dev by Yann Collet · 6 years ago
  3. b8f0f26 Remove unused update on local variable p32 by Wu Xingbo · 6 years ago
  4. 74013b9 Merge pull request #94 from Ashalah/patch-1 by Yann Collet · 6 years ago
  5. 23a889d Fix minor compile error using XXH_ACCEPT_NULL_INPUT_POINTER by Andy Robbins · 6 years ago

xxHash - Extremely fast hash algorithm

xxHash is an Extremely fast Hash algorithm, running at RAM speed limits. It successfully completes the SMHasher test suite which evaluates collision, dispersion and randomness qualities of hash functions. Code is highly portable, and hashes are identical on all platforms (little / big endian).

masterBuild Status
devBuild Status


The benchmark uses SMHasher speed test, compiled with Visual 2010 on a Windows Seven 32-bits box. The reference system uses a Core 2 Duo @3GHz

xxHash5.4 GB/s10Y.C.
MurmurHash 3a2.7 GB/s10Austin Appleby
SBox1.4 GB/s9Bret Mulvey
Lookup31.2 GB/s9Bob Jenkins
CityHash641.05 GB/s10Pike & Alakuijala
FNV0.55 GB/s5Fowler, Noll, Vo
CRC320.43 GB/s9
MD5-320.33 GB/s10Ronald L.Rivest
SHA1-320.28 GB/s10

Q.Score is a measure of quality of the hash function. It depends on successfully passing SMHasher test set. 10 is a perfect score. Algorithms with a score < 5 are not listed on this table.

A new version, XXH64, has been created thanks to [Mathias Westerdahl]'s contribution, which offers superior speed and dispersion for 64-bits systems. Note however that 32-bits applications will still run faster using the 32-bits version. [Mathias Westerdahl]: https://github.com/JCash

SMHasher speed test, compiled using GCC 4.8.2, on Linux Mint 64-bits. The reference system uses a Core i5-3340M @2.7GHz

VersionSpeed on 64-bitsSpeed on 32-bits
XXH6413.8 GB/s1.9 GB/s
XXH326.8 GB/s6.0 GB/s

This project also includes a command line utility, named xxhsum, offering similar features as md5sum, thanks to Takayuki Matsuoka contributions.


The library files xxhash.c and xxhash.h are BSD licensed. The utility xxhsum is GPL licensed.

Build modifiers

The following macros influence xxhash behavior. They are all disabled by default.

  • XXH_FORCE_NATIVE_FORMAT : on big-endian systems : use native number representation, resulting in system-specific results. Breaks consistency with little-endian results.
  • XXH_ACCEPT_NULL_INPUT_POINTER : if presented with a null-pointer, xxhash result is the same as a null-length key, instead of a dereference segfault.
  • XXH_NO_LONG_LONG : removes support for XXH64, useful for targets without 64-bits support.
  • XXH_STATIC_LINKING_ONLY : gives access to state definition for static allocation. Incompatible with dynamic linking, due to risks of ABI changes.
  • XXH_PRIVATE_API : Make all functions static and accessible through xxhash.h for inlining. Do not compile xxhash.c as a separate module in this case.
  • XXH_NAMESPACE : prefix all symbols with the value of XXH_NAMESPACE, in order to evade symbol naming collisions, in case of multiple inclusions of xxHash library (typically via intermediate libraries).

Other languages

Beyond the C reference version, xxHash is also available on many programming languages, thanks to great contributors. They are listed here.

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.