App Bundles & signing

You don't upload an APK anymore

Every APK you've installed so far in this course — via Shift+F10, straight onto an emulator — is a single file containing every resource for every device: every screen density, every CPU architecture. That's fine for local testing, wasteful for a real download.

What you upload to the Play Console instead is an Android App Bundle (.aab) — a publishing format that bundles all of that, unsplit, and hands the splitting job to Google. Play's servers generate optimized, per-device APKs from your one .aab: a Pixel gets only the arm64 native code and xxhdpi images it needs, an older phone gets a smaller, different slice. Same bundle in, a leaner download out for whoever's actually installing it.

One consequence worth knowing: because Play generates the final APK, you can't hand a .aab to a tester and have them just install it the way they could an APK — it has to go through a Play track first (more on tracks in lesson 2), or through bundletool locally for advanced testing.