When you start a new Android project, the build system is one of the most important choices you’ll make. It impacts not just how you build and test your app, but also how your team collaborates, how fast your CI pipeline runs, and how reproducible your releases are.
Think back to the last time you cloned an Android repo onto a fresh machine. Chances are, the first build simply failed. Maybe Gradle pulled in a slightly different library version than CI did. Maybe the Android SDK path wasn’t quite right. Maybe build times crawled because caches had to be rebuilt from scratch. Dependency drift, “works on my machine” errors, and slow iteration cycles are pain points nearly every Android team has felt. Gradle has tried to ease this with features like dependency locking and the Bill of Materials (BOM) approach, but reproducibility and performance at scale are still hard problems.
This is exactly where your choice of build system matters. In the Android ecosystem, that usually means Gradle (the default in Android Studio) or Bazel (Google’s in-house build tool, now open source). Both are powerful in their own right, but designed with very different philosophies and trade-offs. Let us unpack what each tool is, how they compare, and the trade-offs you should be aware of.
Gradle is the official build system for Android Studio. All of Android Studio’s templates, wizards, and tools are designed to generate and work with Gradle projects.
On top of Gradle’s flexible task graph, the Android Gradle Plugin (AGP) adds Android-specific tasks like:
- Resource processing (aapt2)
- Code shrinking and obfuscation (R8/ProGuard)
- Build variants (product flavors + build types)
- ViewBinding/DataBinding
- Native code support (CMake, ndk-build)
- Dynamic Feature Modules and App Bundles (AABs)
Build scripts are written in Groovy or Kotlin DSL, making it approachable for most Android developers.
Bazel is Google’s multi-language, high-performance build system. It was built to handle Google-scale codebases: huge monorepos, millions of build actions, and large distributed teams.
Instead of task graphs, Bazel uses rules declared in Starlark (BUILD and .bzl files). For Android, you use the external rules_android set, which provides targets like android_library, android_binary, and android_instrumentation_test.
Bazel emphasizes:
- Hermetic builds (only declared inputs matter)
- Incremental builds (only rebuild what changed)
- Remote caching (share build outputs across machines)
- Remote execution (offload compilation/tests to a server farm)
This makes it ideal for massive, polyglot projects that need reproducibility and speed at scale.
Build Model & Language
Gradle uses a task-based model that is highly extensible through plugins and configured using either the Groovy or Kotlin DSL. Android-specific behavior is provided by the Android Gradle Plugin (AGP).
Bazel uses a declarative, rule-based model written in Starlark, which is its Python-like extension language. Android support is provided through external rule sets such as rules_android, rules_jvm_external, and rules_kotlin.
Reproducibility & Scale
Gradle can produce reproducible builds if dependency locking is enabled and caching is configured properly, although performance tuning is often required for very large applications.
Bazel enforces hermetic builds through sandboxing and is designed for reproducibility by default, with remote caching and remote execution built in.
Dependency Resolution
Gradle uses a “newest wins” strategy by default—if multiple versions of a library are requested, it automatically selects the latest version. You can override this behavior and ensure consistency by pinning versions with Version Catalogs or lockfiles.
Bazel requires dependencies to be explicit and pinned. Its rules_jvm_external rule generates a maven_install.json lockfile, which prevents accidental version drift.
Build Variants
Gradle treats product flavors and build types as first-class features, making it straightforward to define variants such as debug, release, free, or paid.
Bazel models variants manually using select(), config_setting, and .bazelrc files, which provides more flexibility but is less ergonomic than the flavor system offered by the Android Gradle Plugin (AGP).
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Android-Specific Features
Gradle, through the Android Gradle Plugin (AGP), provides turnkey support for features such as Jetpack Compose, ViewBinding and DataBinding, dynamic feature delivery, App Bundle publishing, and deep IDE integrations.
Bazel supports the core Android build targets and testing frameworks, including Robolectric, but advanced Android features may lag behind or require additional configuration.
Tooling & IDE Integration
Gradle enjoys first-class support in Android Studio, with integrated project templates, Run/Debug configurations, the profiler, “Apply Changes,” and other development features.
Bazel is supported through the IntelliJ/Android Studio Bazel plugin, but it is not officially integrated into Android Studio. As a result, project synchronization and run configurations can be less smooth and may require extra setup.
Build Speed & Cost
Gradle offers decent performance for small to medium projects, especially when features like the Build Cache and Configuration Cache are enabled. However, cold builds (such as cloning a repo for the first time) can still be slow, and scaling performance for very large monorepos often requires significant tuning. Gradle builds are local by default, so speeding them up in CI/CD usually means adding more build agents or investing in Gradle Enterprise for remote caching and analytics.
Bazel is optimized for speed at scale. Its hermetic, incremental build model ensures that only what has changed gets rebuilt, and remote caching allows teams to share build outputs across machines. With remote execution, expensive compilation and testing can be distributed across a build farm, dramatically reducing turnaround times. The trade-off is cost: you need to provision and maintain remote cache/execution infrastructure, which adds operational overhead compared to Gradle’s simpler local-first model. Solutions like the engflow platform can reduce that overhead while optimizing resource utilization and build times even further.
Every build system comes with trade-offs. Gradle and Bazel both excel in different areas, and understanding their strengths and weaknesses helps you decide which one fits your team and project best.
Gradle (with AGP)
Gradle is the default for Android development, tightly integrated with Android Studio and designed to cover the full Android toolchain out of the box. Its ease of use and rich plugin ecosystem make it the fastest way to get started, though scaling performance and reproducibility require extra care.
| Pros | Cons |
|---|
| Easiest to start (one click in Android Studio) | Hermeticity is opt-in, not enforced |
| Full Android feature coverage out of the box | Performance can degrade in very large monorepos |
| Rich dependency management (Maven repos, Version Catalogs) | Dependency resolution defaults to “newest wins,” which can cause drift |
| Build Cache and Configuration Cache improve performance | |
Bazel (with rules_android)
Bazel was built for scale, with reproducibility, incremental builds, and distributed execution as core principles. It requires more setup and tooling investment than Gradle, but for large or polyglot projects, the payoff is faster, more reliable builds, and lower costs in the long run. Bazel especially shines when projects place a premium on quality, since its hermetic and deterministic build model ensures consistent, trustworthy outputs across machines and environments.
| Pros | Cons |
|---|
| Hermetic, reproducible builds by default, guaranteeing consistency and higher build quality | Steeper setup/migration overhead (BUILD files, toolchain registration) |
| Scales to massive projects with remote cache and remote execution | Android Studio support is limited (plugin, not official) |
| Great for polyglot monorepos (Android, backend, web all in one build system) | Some Android-specific features require custom rules in Bazel, and support for new Android tooling often arrives later than in AGP |
Choose Gradle if you are building a typical Android app or library, want the smoothest Android Studio experience, and need quick onboarding for new developers. It provides strong Android-specific support out of the box and is the most efficient choice for small to medium projects.
Choose Bazel if you are working on a larger, more complex project, especially in a polyglot monorepo, where reproducibility, build speed, and quality are at a premium. For big projects, Bazel’s incremental builds, remote caching, and remote execution not only reduce build times but also make builds significantly cheaper to run at scale compared to relying solely on Gradle.
With Gradle, you can create a new project directly in Android Studio, which automatically generates the necessary Gradle and AGP files. From there, you can build, run, and publish App Bundles (AABs) immediately.
With Bazel, you begin by initializing a MODULE.bazel file, adding rules_android and rules_jvm_external, and registering the required SDK and NDK toolchains. You then author your own BUILD files and, if needed, import the project into the IDE using the Bazel plugin for support.
Gradle and Bazel both build Android apps—but they’re designed for different worlds.
Gradle/AGP is the right choice for most Android developers: smooth IDE integration, turnkey Android features, and good-enough performance for small to medium projects.
Bazel shines when your project is huge, your team is large, and build reproducibility and CI performance at scale are critical.
At the end of the day: Gradle gets you moving fast, Bazel keeps you moving fast at scale
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