Non-cryptographic

xxHash3 / XXH128

Designed by Yann Collet (also of LZ4 / Zstandard) and released in 2019, xxHash3 is the third generation of the xxHash family and the fastest non-cryptographic hash in widespread use , tens of GiB/s on a single modern core thanks to SIMD paths, frequently limited by memory bandwidth rather than the algorithm.

Variants

• XXH64 , 64-bit output, the legacy workhorse (2014).
• XXH3 / XXH3_64bits , 64-bit output, 2019 redesign.
• XXH128 / XXH3_128bits , 128-bit output, otherwise identical to XXH3.

At a glance

Where it is used

• Zstandard , content checksums.
• LZ4 frame format , integrity.
• RocksDB, DuckDB, Apache Iceberg , in-memory dedup, partition hashing.
• Rust’s twox-hash crate, the default in many community tools.
• Filesystems / backup tools , e.g., bcachefs uses XXH128 for content addressing.

Why so fast

• Operates on 64-byte stripes that map naturally to AVX2 / AVX-512 / NEON.
• Avoids expensive instructions: no carry-less multiply, no rotate-with-carry, no integer divisions.
• Mostly fused multiply-add and XOR, allowing the CPU’s out-of-order engine to keep wide vector lanes busy.
• Small (~256-byte) inner state, so the hash itself never causes cache pressure even at GB/s rates.

When NOT to use it

xxHash3 is nota cryptographic hash. Differentials are findable in seconds with a SAT solver. Do not use xxHash for content addressing where adversaries could submit inputs, for MACs, or for deduplication that needs to survive an attacker. For those, choose BLAKE3 (often within 2× the speed) or SHA-256.

Try it

xxHash variants are in the comparator catalog; for raw throughput comparisons see the comparator.

References

• xxhash.com , specification and reference benchmarks
• Cyan4973/xxHash , reference implementation
• BLAKE3 · MurmurHash3