# Buck2

Build system, successor to Buck

Repository: https://github.com/facebook/buck2
Canonical: https://ross.abutalabs.com/products/buck2
Homepage: https://buck2.build/
Language: Rust
License: Apache-2.0
License Family: permissive
Last push: 2026-08-26T23:06:29+00:00
Link (homepage): https://buck2.build/
Link (site_page): https://buck2.build/docs
Link (site_page): https://buck2.build/docs/api
Link (site_page): https://buck2.build/docs/prelude/rules
Link (site_page): https://buck2.build/docs/about/why

## Health v2 (maintenance only)
Score: 86/100 (v2, computed 2026-09-03T02:20:16.233290+00:00)
- activity 99, release rhythm 60, longevity 100
- inputs: {"age_days": 1685, "days_push": 7, "days_rel": 12, "gap_med": 14, "n_releases_24m": 46}
- flags: prerelease_only
- formula: round(0.45*activity + 0.35*rhythm + 0.20*longevity); archived -> min(score, 10)

## Adoption (not part of the score)
Stars 4406, forks 389 (observed 2026-08-28T04:08:48.406449+00:00)

## What it is
Buck2 is Meta's fast, extensible, large-scale build system written in Rust, succeeding the original Buck (whose repository is now dead). It supports many languages (C++, Python, Rust, Java, Kotlin, Go, Haskell, OCaml, Erlang) with hermetic, Starlark-defined rules and remote build execution.

## Use cases
- build a large multi-language monorepo
- replace make or bazel with a faster build system
- write custom build rules in starlark
- set up remote build execution and caching
- build c++ rust and java projects with one tool
- run ci that only builds what changed

## When to choose
- you maintain a large monorepo spanning multiple languages
- you need hermetic, reproducible builds with remote execution
- you want extensible build rules written in Starlark
- build speed on large codebases is a priority

## When to avoid
- you have a small single-language project where simpler tools suffice
- you need a mature ecosystem of third-party rules like Bazel's
- you rely on the original Buck - that repository is dead and unmaintained
- your team cannot invest in learning a new build system

## Facets
- artifact type: cli-tool
- maturity: active
- function: build-tool, cli, developer-tools
- domain: developer-tools, cross-platform
- platform: windows, cli, rust
- tags: starlark, monorepo, remote-execution, hermetic-builds, multi-language, bazel-alternative, incremental-build, command-line, linux, macos

## Member repositories
- facebook/buck2 (main) score 86
- facebook/buck (mirror) score 10

## Provenance
- Observed fields: from GitHub, fetched 2026-08-28T04:08:48.406449+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 2026-08-29T17:26:20.413532+00:00, confidence not recorded.
  - readme: https://github.com/facebook/buck2 (fetched 2026-08-28T04:08:48.406449+00:00, sha 31881a3712b9)
  - homepage: https://buck2.build/ (fetched 2026-08-29T08:26:46.095815+00:00, sha 349a3d7ca50e)
  - site_page: https://buck2.build/docs (fetched 2026-08-29T08:26:46.117688+00:00, sha a9b475578f3b)
  - site_page: https://buck2.build/docs/api (fetched 2026-08-29T08:26:46.130287+00:00, sha f97c89014d64)
  - site_page: https://buck2.build/docs/prelude/rules (fetched 2026-08-29T08:26:46.132222+00:00, sha 44973e6f463f)
  - site_page: https://buck2.build/docs/about/why (fetched 2026-08-29T08:26:46.133944+00:00, sha d5e0a754eae4)
  - site_page: https://buck2.build/docs/getting_started (fetched 2026-08-29T08:26:46.135817+00:00, sha ccbda43e6972)
  - registry_crates: https://crates.io/api/v1/crates/buck2 (fetched 2026-08-29T08:26:46.137559+00:00, sha f1464221c528)
- Data as of 2026-08-30T08:39:29.467469+00:00.