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Cyan4973/xxHash

A C library for extremely fast non-cryptographic hashing, producing identical 32, 64 and 128-bit hashes across platforms.

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What is it?

xxHash is a non-cryptographic hash algorithm written in C, aimed at workloads where hashing speed matters, such as hash tables, bloom filters, checksums and data deduplication. It is portable and produces identical results on little-endian and big-endian systems, and its outputs stay stable across releases once finalized.

The library provides XXH32, XXH64 and XXH3, with XXH3 offering both 64-bit and 128-bit (XXH128) variants using vectorized arithmetic. XXH3_64bits() is the recommended default for new applications. The project also includes the xxhsum command line tool for generating and verifying checksums, and a header-only mode via XXH_INLINE_ALL.

xxHash is not suitable for signatures, password storage or any security-sensitive purpose. Its build options cover inlining, endianness, memory access methods, and binary size reduction for embedded or constrained targets.

Key features

  • 01Non-cryptographic hashes in 32-bit, 64-bit and 128-bit widths.
  • 02Identical output on little-endian and big-endian platforms.
  • 03Vectorized XXH3 and XXH128 implementations with AVX2 and SSE2 paths.
  • 04Streaming API for hashing inputs of unknown size.
  • 05Header-only integration through XXH_INLINE_ALL.
  • 06Build macros to shrink binary size or disable features for embedded targets.

Use cases

  • Keying entries in hash tables or bloom filters where speed on small inputs matters.
  • Computing fast checksums for files with the xxhsum command line tool.
  • Detecting duplicate data blocks in storage or deduplication pipelines.
  • Embedding a fast hash in performance-sensitive C or C++ applications.

Quick start

  1. 1

    Build the library and xxhsum CLI with make

    make
  2. 2

    Hash this README file with XXH3 using xxhsum

    ./xxhsum -H3 README.md

Things to know

  • xxHash is not a cryptographic hash and must not be used for signatures or password storage.
  • The license is listed as NOASSERTION in the metadata, so check the repository license file before use.

Topics

#hash-function#checksum#non-cryptographic#performance#hash-table#data-structures#dispersion#hash#hash-checksum#hash-functions

FAQ

What is xxHash?
A C library for extremely fast non-cryptographic hashing, producing identical 32, 64 and 128-bit hashes across platforms. xxHash is a non-cryptographic hash algorithm written in C, aimed at workloads where hashing speed matters, such as hash tables, bloom filters, checksums and data deduplication. It is portable and produces identical results on little-endian and big-endian systems, and its outputs stay stable across releases once finalized.
Is xxHash free to use? What license does it have?
xxHash is open source under the Other license. Check the license terms before using it in commercial products.
Is xxHash still maintained?
Actively maintained. The last commit to xxHash was on Oct 29, 2026.
What can I use xxHash for?
Keying entries in hash tables or bloom filters where speed on small inputs matters. Computing fast checksums for files with the xxhsum command line tool. Detecting duplicate data blocks in storage or deduplication pipelines. Embedding a fast hash in performance-sensitive C or C++ applications.
How do I install xxHash?
Build the library and xxhsum CLI with make: make Hash this README file with XXH3 using xxhsum: ./xxhsum -H3 README.md
Where can I get xxHash?
The source code and installation instructions are on GitHub: https://github.com/Cyan4973/xxHash

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