bazelbuild/bazel

Bazel is a build system, a tool that takes your source code and turns it into runnable software, handling compilation, linking, testing, and all the steps in between. Its tagline is "Fast, Correct, Choose two," meaning it delivers both speed and reliability where many traditional build tools force a trade-off. The key to Bazel's speed is that it only rebuilds what has actually changed. If you modify one file in a large codebase, Bazel rebuilds only the parts of the project that depend on that file, skipping everything else. It does this through precise dependency tracking, it knows exactly what each piece of code depends on, so nothing is rebuilt unnecessarily. It also supports distributed caching, meaning build results can be shared across a whole team: if a colleague already built the same code, you download their cached result instead of rebuilding. Bazel supports multiple programming languages in a single project, including Java, C++, Android, iOS, and Go, making it well-suited for large companies or open-source projects with mixed-language codebases. It is designed to scale from small projects to massive "monorepos" (a single repository containing millions of files and many teams' code). The system is extensible via a scripting language, allowing teams to add support for new languages and platforms. You would use Bazel if you work on a large codebase where build times have become a bottleneck, or if your project spans multiple languages and needs a consistent, reliable build and test workflow across platforms. The tech stack is Java.