Parallel Bits - Which Parts of Gradle Run in Parallel

By default, nearly the entire invocation of Gradle is done serially, but there are ways to make it partially parallel.

The list is ordered from the mostly safe to less stable options.

Parallel task execution for tasks in separate projects

Historically, enabled when using Gradle Parallel Execution mode with org.gradle.parallel=true, but now it is also achieved by enabling Gradle configuration caching feature with org.gradle.configuration-cache=true. Configuration cache enables stricter rules in the build and therefore is safer to use than the parallel execution mode.

Parallel task execution for tasks within the same project

Enabling Gradle configuration caching feature with org.gradle.configuration-cache=true. Note, despite org.gradle.parallel=true sounding like it would do this, it does not in fact enable this except for a narrow set of tasks that use Gradle worker API

Parallel execution for workers within a single task

Implement tasks using Gradle worker API and enable either Gradle configuration caching feature with org.gradle.configuration-cache=true or Gradle Parallel Execution mode with org.gradle.parallel=true.

Parallel IDE model building during Gradle Sync

Enabling Gradle Parallel Execution mode with org.gradle.parallel=true and using Android Studio Electric Eel or newer.

Parallel test execution within a JVM test task

Setting the number of parallel forks via Test.setMaxParallelForks.

Parallel Android Gradle Plugin R8 task execution

Setting android.r8.maxWorkers

Parallel Configuration Cache loading

Enabling Gradle configuration caching feature with org.gradle.configuration-cache=true does this automatically as long as you use Gradle 8.11 or newer.

Parallel Configuration Cache storing

Enabling Gradle configuration cache parallel store feature with org.gradle.configuration-cache.parallel=true when using Gradle 8.11 or newer. Partially unsafe as it requires build logic and all plugins to avoid reaching cross-projects while configuring projects.

build.gradle(.kts) compilation

Enable Gradle Isolated Projects feature with org.gradle.unsafe.isolated-projects=true. Quite unsafe as Isolated Projects is still incubating.

Parallel configuration of projects

Enable Gradle Isolated Projects feature with org.gradle.unsafe.isolated-projects=true. Quite unsafe as Isolated Projects is still incubating.

I hope this helps you get a sense of the toggles you have to control the Gradle build parallelism.