What is an AAB Builder?
An AAB builder creates Android App Bundle files, the publishing format required by Google Play since August 2021. Unlike APK files, AABs let Google Play generate optimized APKs for each device configuration, reducing download sizes by an average of 15% compared to universal APKs.
The Android App Bundle format includes all compiled code and resources but defers APK generation to Google Play. This means users download only the code, resources, and native libraries they need for their specific device, language, and screen density.
Building AAB files traditionally requires Android Studio and a properly configured Gradle build. Fastshot eliminates this requirement by generating your app code with AI and compiling AAB files entirely in the cloud.
With Fastshot, you go from an app idea to a Google Play-ready AAB without installing any development tools. The generated source code is yours to keep, and the AAB meets all of Google Play current publishing requirements.
How the AAB Builder Works
Describe Your App
Tell Fastshot about the app you want to publish on Google Play. Describe screens, features, and user flows in plain English.
AI Generates the Codebase
Fastshot creates a complete React Native + Expo project with optimized components, navigation, and Supabase backend integration.
Cloud Builds Your AAB
The build pipeline compiles your project into an Android App Bundle, applying code signing and optimization for Google Play distribution.
Upload to Google Play Console
Take the AAB file and upload it directly to Google Play Console. Google Play handles device-specific APK generation and distribution.
AAB Builder Capabilities
Google Play Compliant
AAB files meet all current Google Play publishing requirements, including the mandatory App Bundle format for new app submissions.
Optimized App Delivery
AAB format enables Google Play Dynamic Delivery, which generates device-specific APKs that are smaller and faster to install.
Play Asset Delivery
Large assets can be delivered on-demand or during installation through Play Asset Delivery, supported natively by the AAB format.
Automatic Code Signing
Cloud builds handle upload key signing. Combined with Google Play App Signing, your releases are secured end to end.
Resource Optimization
The AAB format strips unused resources per device, including unnecessary screen density assets and language files, reducing installed size.
APK Fallback Available
Need an APK for testing or sideloading? Generate both AAB and APK from the same project with a simple configuration switch.
AAB vs APK: Which Do You Need?
| Aspect | AAB (Android App Bundle) | APK (Android Package Kit) |
|---|---|---|
| Google Play required | Yes (mandatory since 2021) | No longer accepted for new apps |
| Sideloading | Not directly installable | Directly installable on devices |
| Download size | ~15% smaller (device optimized) | Universal, larger download |
| Asset delivery | On-demand and install-time options | All assets bundled upfront |
| Code signing | Google Play App Signing | Self-signed or custom keystore |
| Best for | Google Play distribution | Testing, sideloading, alt stores |
AAB Builder FAQ
About the Author
Elvira Dzhuraeva is an expert in AI mobile app development and React Native. A former Senior Product Manager at Google specializing in AI/ML and Generative AI, she is the Founder of Fastshot (YC-backed) and a founding contributor to Kubeflow.