Why Bazel?

Bazel is a fast, correct, and extensible build tool with integrated testing that supports multiple languages, repositories, and platforms in an industry-leading ecosystem.

Bazel is fast

Bazel knows exactly what input files each build command needs, avoiding unnecessary work by re-running only when the set of input files have changed between each build. It runs build commands with as much parallelism as possible, either within the same computer or on remote build nodes. If the structure of build allows for it, it can run thousands of build or test commands at the same time.

This is supported by multiple caching layers, in memory, on disk and on the remote build farm, if available. At Google, we routinely achieve cache hit rates north of 99%.

Bazel is correct

Bazel ensures that your binaries are built only from your own source code. Bazel actions run in individual sandboxes and Bazel tracks every input file of the build, only and always re-running build commands when it needs to. This keeps your binaries up-to-date so that the same source code always results in the same binary, bit by bit.

Say goodbye to endless make clean invocations and to chasing phantom bugs that were in fact resolved in source code that never got built.

Bazel is extensible

Harness the full power of Bazel by writing your own rules and macros to customize Bazel for your specific needs across a wide range of projects.

Bazel rules are written in Starlark, our in-house programming language that’s a subset of Python. Starlark makes rule-writing accessible to most developers, while also creating rules that can be used across the ecosystem.

Integrated testing

Bazel’s integrated test runner knows and runs only those tests needing to be re-run, using remote execution (if available) to run them in parallel. Detect flakes early by using remote execution to quickly run a test thousands of times.

Bazel provides facilities to upload test results to a central location, thereby facilitating efficient communication of test outcomes, be it on CI or by individual developers.

Multi-language support

Bazel supports many common programming languages including C++, Java, Kotlin, Python, Go, and Rust. You can build multiple binaries (for example, backend, web UI and mobile app) in the same Bazel invocation without being constrained to one language’s idiomatic build tool.

Multi-repository support

Bazel can gather source code from multiple locations: you don’t need to vendor your dependencies (but you can!), you can instead point Bazel to the location of your source code or prebuilt artifacts (e.g. a git repository or Maven Central), and it takes care of the rest.

Multi-platform support

Bazel can simultaneously build projects for multiple platforms including Linux, macOS, Windows, and Android. It also provides powerful cross-compilation capabilities to build code for one platform while running the build on another.

Wide ecosystem

Industry leaders love Bazel, building a large community of developers who use and contribute to Bazel. Find a tools, services and documentation, including consulting and SaaS offerings Bazel can use. Explore extensions like support for programming languages in our open source software repositories.