Convert ZIP to AAR

An Android library may be distributed as a ZIP even though Android Studio or Gradle requires an AAR dependency. The required action is either rebuilding the library project or confirming that the ZIP already has the AAR layout; changing .zip to .aar is not normally a conversion.

What the ZIP format is

ZIP is a general-purpose archive format for bundling and compressing files. Developers use it for Android source projects, SDK packages, sample code, compiled files, and release distributions; Windows, macOS, Linux, 7-Zip, and build systems can create and extract it.

ZIP imposes no Android-specific directory structure. Inspect the archive before choosing a conversion method: it may contain a complete Gradle project, an already packaged library, source files, or unrelated files.

What the AAR format is

AAR, or Android Archive, is the package format produced for an Android library module. Android Gradle Plugin and Android Studio can use it as a local dependency, and a Maven repository can distribute it with its accompanying metadata.

An AAR is technically a ZIP file with an Android library layout. A normal AAR contains AndroidManifest.xml, classes.jar, res/, and R.txt; it may also contain assets/, jni/, libs/, prefab/, public.txt, proguard.txt, lint.jar, and other supported entries. It can package compiled Java or Kotlin bytecode, Android resources, manifest declarations, native libraries, and consumer R8 or ProGuard rules. Unlike a plain JAR, it can carry Android resources and native components.

How to convert a ZIP containing a library project

1. Extract the ZIP with 7-Zip, the system archive utility, or Android Studio. Find settings.gradle or settings.gradle.kts and a module containing build.gradle or build.gradle.kts.
2. Confirm that the target module applies the Android library plugin, such as com.android.library, rather than com.android.application. Do not change an application module to a library without checking its manifest, dependencies, and build configuration.
3. Open the extracted project in Android Studio, install the SDK and build-tools versions requested by the project, and allow Gradle synchronization to complete. Resolve missing repositories, plugins, and dependencies before building.
4. Build the release variant from Android Studio with Build → Make Project, or run the module task from the project directory:

./gradlew :library:assembleRelease

On Windows, run gradlew.bat :library:assembleRelease. Replace library with the actual module name. The output is normally under library/build/outputs/aar/, for example library-release.aar. Use the debug task only when a debug AAR is specifically required.

How to handle a ZIP that is already an AAR

Open the archive with 7-Zip or another archive utility and inspect its top level. If it has the AAR structure, including AndroidManifest.xml, classes.jar, res/, and R.txt, it may have been given the wrong extension. Make a copy and rename it:

mv library.zip library.aar

On Windows:

ren library.zip library.aar

If the files are nested inside an extra directory, repackage the contents so those entries are at the archive root. Renaming or repacking does not compile source, process resources, generate R.txt, or add a manifest. Test the resulting AAR in a small Android application.

How to handle source or arbitrary files

A ZIP containing only .java, .kt, .class, documents, or arbitrary folders cannot be converted reliably by an archive converter. Create or open an Android library module, place source under src/main/java/ or src/main/kotlin/, place resources under src/main/res/, place assets under src/main/assets/, configure the manifest and dependencies, and run assembleRelease.

Native files must use the expected ABI directories, such as src/main/jniLibs/arm64-v8a/. The Android Gradle Plugin must compile the code and resources; a general ZIP utility cannot perform these steps.

Desktop and online tools

Android Studio with Gradle is the appropriate desktop option when the ZIP contains source or a Gradle project. 7-Zip, Finder, File Explorer, and command-line unzip or zip are suitable for inspection and simple repackaging.

Online archive services such as CloudConvert or Zamzar may support generic ZIP repackaging or extension conversion, but they cannot resolve Android dependencies or build an AAR. Use an online service only for a non-confidential archive that already has the correct AAR contents; do not upload proprietary source, SDKs, signing material, or private libraries.

Compatibility checks

Before distributing the result, open the AAR as a ZIP and verify its manifest, classes.jar, resources, native libraries, assets, and consumer rules. Test it with the consuming project’s Android Gradle Plugin, compile SDK, Kotlin version, and supported device ABIs.

An AAR does not automatically bundle every external Maven dependency. Consumers may need to declare those dependencies separately, and a local file dependency does not provide the dependency metadata that a Maven publication supplies. Add a local AAR with a Gradle dependency such as implementation files('libs/library-release.aar'), or publish the AAR to a Maven repository with its POM and module metadata.