# rust-lang/hashbrown

Rust port of Google's SwissTable hash map

Repository: https://github.com/rust-lang/hashbrown
Canonical: https://ross.abutalabs.com/products/hashbrown
Homepage: https://rust-lang.github.io/hashbrown
Language: Rust
License: Apache-2.0
License Family: permissive
Last push: 2026-08-10T18:12:47+00:00

## Health v2 (maintenance only)
Score: 88/100 (v2, computed 2026-09-03T02:20:16.233290+00:00)
- activity 97, release rhythm 71, longevity 100
- inputs: {"age_days": 2866, "days_push": 23, "days_rel": 116, "gap_med": 49.0, "n_releases_24m": 7}
- flags: none
- formula: round(0.45*activity + 0.35*rhythm + 0.20*longevity); archived -> min(score, 10)

## Adoption (not part of the score)
Stars 2983, forks 357 (observed 2026-08-28T04:07:33.925009+00:00)

## What it is
hashbrown is a Rust port of Google's SwissTable hash map, serving as a drop-in replacement for the standard library's HashMap and HashSet. It is the implementation adopted by Rust's std HashMap and can also be used directly, including in no_std environments with an allocator.

## Use cases
- replace std HashMap with a faster hash map in Rust
- use a hash map in a no_std embedded or kernel environment
- reduce memory overhead of hash tables in Rust
- get faster hash set lookups with SIMD
- choose a custom or faster default hasher for hash maps

## When to choose
- you need a high-performance HashMap/HashSet in Rust, roughly 2x faster than the old std implementation
- you are targeting no_std environments like embedded systems or kernels with a global allocator
- you want lower per-entry memory overhead (1 byte vs 8)
- you need serde or rayon support for hash containers

## When to avoid
- you need strong HashDoS resistance by default, since foldhash is weaker than SipHash
- you just use std HashMap and don't need no_std or custom hasher control
- you rely on the deprecated RawEntry API as a primary feature

## Facets
- artifact type: library
- maturity: stable
- function: caching, developer-tools
- domain: performance, developer-tools
- platform: rust, embedded, cross-platform
- tags: hashmap, swisstable, hash-table, no-std, simd, data-structures, algorithms

## Member repositories
- rust-lang/hashbrown (main) score 88

## Provenance
- Observed fields: from GitHub, fetched 2026-08-28T04:07:33.925009+00:00.
- Health v2: computed from the inputs above; adoption is never an input.
- Inferred fields (summary, facets, guidance): AI-extracted, prompt v1, taxonomy v1, on 2026-08-30T07:31:27.753402+00:00, confidence not recorded.
  - readme: https://github.com/rust-lang/hashbrown (fetched 2026-08-28T04:07:33.925009+00:00, sha 160af226833b)
  - homepage: https://rust-lang.github.io/hashbrown (fetched 2026-08-29T09:46:29.512383+00:00, sha a8ce097f12cb)
  - registry_crates: https://crates.io/api/v1/crates/hashbrown (fetched 2026-08-29T09:46:29.521658+00:00, sha 6dae7698880f)
- Data as of 2026-08-30T08:39:29.467469+00:00.