Android App Bundle (.aab) is Google's preferred publishing format. AAB contains compiled code and resources without APK packaging. Google Play generates optimized APKs per device configuration. Dynamic delivery splits features into on-demand modules. Configuration APKs target specific screen densities and CPU architectures. App Bundle reduces app size by an average of 20%. Instant-enabled apps users try features without installation. In-app updates deliver features without full app update. Play Asset Delivery manages large game assets efficiently. APK remains the format for direct distribution outside Play Store. AAB to APKs for testing. App Signing by Google Play enables flexible key management. App Bundle supports feature modules for modular architecture. On-demand delivery downloads features only when needed. Conditional delivery excludes features on incompatible devices. Fusing creates monolithic APKs for devices without split APK support. App Bundle testing requires bundletool or internal test tracks. Migration from APK to AAB is straightforward. App Bundle is mandatory for new apps on Google Play. Legacy APK publishing remains available for existing apps.