AAB+PAD Conversion and Repackaging: From Android App Bundle to APK and Back

Background : Since August 2021 Google Play requires the Android App Bundle (AAB) format and enforces a 150 MB size limit. To deliver larger assets without exceeding this limit, developers must use Play Asset Delivery (PAD).

Problem : Existing APK‑centric split pipelines cannot handle AAB+PAD packages. After integrating PAD, only AAB packages can be produced, so the old split process becomes obsolete. The goal is to split an AAB+PAD package, upgrade SDK code, and keep PAD resources.

Basic Idea : Convert the AAB+PAD into an APK, reuse the legacy split logic on the APK, then convert the split result back into an AAB that still contains PAD.

Step 1 – Extract PAD resources : An AAB with PAD has a directory structure similar to:

├── base/
    ├── dex/
    ├── ...
├── base_assets/   ← PAD asset pack (name may vary)
    ├── assets/
    ├── assets.pb
    ├── manifest/
        ├── AndroidManifest.xml
├── BundleConfig.pb
├── META-INF/

The PAD resources are the assets/ folder and the manifest/AndroidManifest.xml inside the asset‑pack folder. Create a zip (e.g., pad.zip ) with the following layout:

// pad.zip (name arbitrary)
├── assets/
├── manifest/
    ├── AndroidManifest.xml

Step 2 – Convert AAB+PAD to APK : Use bundletool to generate a universal APK that contains all code and resources, including PAD.

java -jar bundletool.jar build-apks --mode=universal --bundle=my_app.aab --output=my_app.apks

Unzip my_app.apks to obtain universal.apk , which is the APK version of the original AAB+PAD.

Step 3 – Split the APK : Apply the existing APK split pipeline to universal.apk . The result should be a base.zip that contains the main code **without** PAD resources (the PAD assets have already been merged into the APK and will be removed from base.zip to avoid conflicts).

Step 4 – Rebuild AAB with PAD : Combine the base.zip (code only) and the previously saved pad.zip (PAD assets) to produce a new AAB that retains the PAD module.

java -jar bundletool.jar build-bundle --modules=base.zip,pad.zip --output=my_fixed.aab

Verification : Validate the final AAB and ensure the PAD asset pack is present.

java -jar bundletool.jar validate --bundle=my_fixed.aab

The validation output should list the PAD asset pack (e.g., base_assets ) under “Asset packs”, confirming that the AAB still contains the required PAD resources and can be uploaded to Google Play.