Bazel is an advanced, open-source build and test automation tool designed to handle the demands of modern, large-scale software development. Engineered to streamline workflows, Bazel reduces build times, improves reliability, and ensures consistent, reproducible results across diverse environments—helping teams deliver high-quality software faster.
In this comprehensive guide, we’ll explore what Bazel is, its key features, how it originated, why it stands out in today’s development landscape, and who’s harnessing its power. Whether you’re working on a sprawling monorepo, juggling complex dependencies, or simply seeking a more scalable build solution, Bazel may be the tool you need.
What Is Bazel?
Bazel is a build and test system that automates compiling, testing, and packaging software projects. Similar to tools like Make, Maven, or Gradle, Bazel manages every step of the build process. However, it differentiates itself by excelling at scale: Bazel easily handles massive codebases, intricate dependency graphs, and multi-language builds—all while maintaining speed and consistency.
Built for a world where codebases span multiple repositories and platforms, Bazel enforces a strict, declarative build approach using a language called Starlark. This approach ensures reproducible builds, empowering teams to ship stable, production-ready code reliably.
Key features of Bazel
1. High performance and scalability
Bazel is designed from the ground up for speed. It uses parallel execution, advanced caching, and remote build capabilities to scale effortlessly to codebases with millions of lines of code. Whether you’re working on a small project or a massive monorepo, Bazel delivers consistently fast feedback loops.
2. Incremental and targeted builds
With Bazel, you only rebuild what’s changed. By analyzing dependency graphs, Bazel identifies precisely which parts of the code require recompilation or re-testing. This targeted approach accelerates development, reducing unnecessary work and slashing iteration times.
3. Reproducible and reliable
Say goodbye to the “works on my machine” problem. Bazel ensures build reproducibility by using deterministic build rules and clean dependency isolation. Whether you’re running builds locally, in a CI/CD pipeline, or across remote build clusters, you’ll get consistent, stable results every time.
4. Multi-Language and cross-platform support
Bazel natively supports a wide range of programming languages, including Java, C++, Go, Python, TypeScript, Rust, and more. Its extensibility allows you to integrate new languages or platforms seamlessly. This polyglot flexibility makes Bazel an ideal choice for teams that embrace diverse technologies.
5. Extensibility through Starlark
The heart of Bazel is the Starlark language, a Pythonic configuration language that developers can use to define custom build rules. With Starlark, you gain full control over your build processes, enabling you to adapt Bazel to your unique project requirements.
6. Remote caching and execution
Modern software development often involves distributed teams and complex infrastructure. Bazel’s remote caching and remote execution features let you share build outputs and delegate tasks to remote workers, significantly speeding up builds and tests at scale.
Origins: From Blaze to Bazel
Bazel’s story begins at Google, where the search giant developed an internal system called “Blaze” to handle its ever-growing, complex codebase. As Google scaled, it needed a tool capable of managing millions of lines of code, thousands of engineers, and a near-infinite web of dependencies—all while ensuring builds were fast, safe, and reproducible.
In 2015, Google open-sourced Blaze as Bazel, allowing the wider software community to benefit from its innovations. Today, Bazel is jointly shaped by Google’s engineers and the global open-source community, ensuring it continually evolves to meet modern software challenges.
Who uses Bazel today?
Bazel’s adoption has grown far beyond Google’s walls, capturing the attention of startups, enterprises, and open-source projects alike. Here are a few well-known organizations and technologies leveraging Bazel:
- Google: As its originator, Google continues to rely heavily on Bazel to build and maintain some of the world’s most complex software systems.
- Angular: The popular Angular framework uses Bazel to streamline builds and tests for front-end projects, ensuring performance and reproducibility.
- TensorFlow: Google’s machine learning library, TensorFlow, employs Bazel to manage its intricate dependencies and maintain efficient builds for data-intensive workloads.
- Dropbox: By adopting Bazel, Dropbox has simplified multi-platform, multi-language builds, reducing complexity and accelerating release cycles.
Why Bazel matters in 2024
As codebases balloon in size, complexity, and language diversity, traditional build systems often struggle to keep up. Bazel meets these modern challenges head-on. By combining speed, scalability, and reproducibility, Bazel empowers teams to:
- Shorten feedback loops: Rapid incremental builds ensure developers spend less time waiting and more time coding.
- Increase reliability: Deterministic builds reduce unexpected failures and dependency issues.
- Improve developer productivity: A single, unified build system across the organization simplifies onboarding, tooling, and maintenance.
- Enhance continuous integration and delivery: Consistent builds enable fully automated CI/CD pipelines, supporting rapid and reliable releases.
Beyond the build with Graphite
While Bazel optimizes your build and test processes, consider complementing it with a tool like Graphite to streamline code review workflows and improve your release cadence. Graphite helps developers break down large changes into manageable, reviewable chunks and provides a clear visual interface for comparing branches and understanding commit histories. By integrating Graphite into your workflow:
- Faster code reviews: Reduce friction and accelerate feedback by making review processes simpler and more transparent.
- Higher code quality: Encourage smaller, more incremental changes that are easier to test, review, and merge—perfectly aligning with Bazel’s incremental build philosophy.
- Enhanced developer velocity: Combine Bazel’s rapid, reproducible builds with Graphite’s streamlined code review and branching strategy, creating an environment where developers can ship high-quality code at top speed.
In an ecosystem where time-to-market and code quality can make or break success, leveraging Bazel for build optimization and Graphite for efficient code reviews gives you a powerful, end-to-end workflow advantage. Together, they help ensure that your software development pipeline is not only fast and reliable, but also continuously improving—ultimately enabling your team to innovate and deliver value more swiftly than ever.