Bazel Build Tool

Bazel is a fast and correct build and test tool originally developed at Google and released as open source under the Apache 2.0 license. It supports multiple programming languages including Java, C++, Go, Python, Rust, Android, and iOS, enabling teams to build monorepos containing diverse technology stacks with a single unified build system. The tool runs on Windows, macOS, and Linux with full cross-platform reproducibility. Speed is achieved through two key mechanisms: local caching that stores build outputs and skips redundant work, and distributed caching that shares build results across development machines and CI systems via remote execution backends. An optimized dependency analysis engine tracks only changed inputs, rebuilding only what is necessary rather than the entire project. Builds are fully parallelized across available CPU cores, and the hermetic build approach ensures that builds are isolated from the host environment, producing identical outputs regardless of where they run. Trusted by Google internally for building their entire codebase of billions of lines of code, as well as by Stripe, Dropbox, Uber, Pinterest, and many other technology companies. The tool uses a declarative build language called Starlark for defining build targets and rules, which is a deterministic subset of Python. BUILD files specify targets, dependencies, and build rules in a human-readable format that integrates with version control. Bazel integrates with CI systems including Jenkins, GitHub Actions, and Buildkite, and supports remote build execution for horizontal scaling.