Buck2
Claim this toolA high-performance, extensible build system designed for large, multi-language monorepos.
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Tracked since 2026
The Bottom Line
- Price
- Free, no paid tier. Compare plans
Key facts
- Significantly faster build times compared to its predecessor, especially for large projects.
- Ensures reliable builds through hermetic rules and strict dependency enforcement.
- Highly extensible with all build rules written in Starlark, allowing custom rule definition.
Pros
- Optimized for very large, multi-language monorepos
- Provides highly reliable and reproducible builds
- Allows for rapid iteration and customization of build rules
- Leverages remote execution for increased parallelism and efficiency
- Language-agnostic core binary ensures consistent feature access for all rules
Cons
- Designed for large-scale use cases, potentially complex for smaller projects
- Requires understanding of Starlark for custom rule development
What is Buck2?
Buck2 is a build system developed by Meta, specifically engineered to handle the complexities of very large monorepos that incorporate multiple programming languages such as C++, Python, Rust, Kotlin, and Swift. It is a complete rewrite of its predecessor, Buck1, aiming to improve speed, reliability, and extensibility while retaining target compatibility. Buck2 addresses the limitations of traditional build systems like Make when dealing with the scale and diversity of modern large-scale software development.
Key aspects of Buck2 include its ability to query build targets, support for remote execution to significantly increase parallelism, and multi-language composability, allowing different language components to interact seamlessly. It integrates with file watching services for efficient change detection and utilizes Starlark, a Python-like language, for defining build targets and advanced manipulations. Written in Rust, Buck2 prioritizes remote execution and features an entirely language-agnostic binary, with all rules defined externally in Starlark, enabling faster iteration and consistent feature availability across all rules.
Available on: Web
Louis Corneloup Source buck2.build ↗
Key Features
- Faster build performance
- Hermetic build rules by default
- Extensible with Starlark-defined rules
- Remote execution first architecture
- Multi-language composability
- Dynamic (monadic) graph computation engine
- Support for dynamic dependencies and anonymous targets
- Written in Rust for performance and absence of GC pauses
Pricing
Free
Buck2 is completely free to use with no hidden costs.
Reviews
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Buck2 FAQ
How does Buck2 handle projects with multiple programming languages?
Buck2 is designed for multi-language composability, allowing different language components like C++, Python, Rust, Kotlin, and Swift to interact seamlessly within a single monorepo. Its language-agnostic core binary ensures consistent feature access across all build rules, regardless of the programming language.
Which teams would benefit most from using Buck2?
Buck2 is best suited for teams managing very large, multi-language monorepos due to its optimization for scale and complexity. It provides highly reliable and reproducible builds, which is crucial for large-scale software development.
How does Buck2 compare to Bazel?
Buck2, like Bazel, is a build system designed for large monorepos, but Buck2 is a complete rewrite of its predecessor, Buck1, aiming for improved speed, reliability, and extensibility. It prioritizes remote execution and uses Starlark for defining build targets, similar to Bazel's approach.
What kind of limitations might a user encounter with Buck2?
Buck2 is primarily designed for large-scale use cases, which might introduce complexity for smaller projects. Additionally, users will need to understand Starlark to develop custom build rules effectively.
How is Buck2 priced?
Buck2 is free to use, and no paid plan is required to access its features or capabilities.
Can Buck2 improve build times for large projects?
Yes, Buck2 leverages remote execution to significantly increase parallelism, which can lead to faster build times for large projects. It also integrates with file watching services for efficient change detection, further optimizing the build process.
How does Buck2 allow for customization of build rules?
Buck2 uses Starlark, a Python-like language, for defining build targets and advanced manipulations. This enables rapid iteration and customization of build rules, allowing users to tailor the build process to their specific needs.
Source: buck2.build