From project to APK on a real phone

the short answer

How do I build an APK and get it onto an Android phone?

Install the Android Build Support module, switch the platform to Android, set a package name of your own, and build. What stops most first builds is an SDK or JDK path Unity cannot find; what bites later is shipping the default com.DefaultCompany package name, because a package name can never change once the app is on Google Play.

Getting an APK onto a phone is four steps and two traps. The steps take twenty minutes the first time; the traps are what turn that into an afternoon.

1 — Install Android Build Support

1
Open Unity Hub, go to Installs, and use the gear menu on your Unity version to add modules.
2
Tick Android Build Support, and both items nested underneath it: the SDK & NDK Tools and the OpenJDK. All three, not just the first.
3
It downloads a few gigabytes. Let it finish before opening the project, or the platform list will still show Android as unavailable.

2 — Switch the platform

Switching platform re-imports every texture in the project into a format Android can read. On a small project it takes a minute; on a large one it is worth starting before you make coffee. It only happens once per platform.

1
Open File▸Build Profiles (called Build Settings before Unity 6), pick Android, and press Switch Platform.
2
Press Add Open Scenes with every scene you want in the build open. A scene that is not on this list does not exist in the built game.
3
The scene at index 0 is the one the game starts on. Drag it to the top if it is not already there.

3 — Player Settings that actually matter

Package Name — change it. The default com.DefaultCompany.ProjectName installs fine for testing, but the package name is your app's permanent identity on Google Play: it can never be changed after the app is published.
Minimum API Level — 24 or higher covers effectively every phone in use and avoids a pile of compatibility work.
Scripting Backend IL2CPP and Target Architectures ARM64 — the Play Store has required 64-bit for years. Mono and ARMv7 alone will be refused at upload.

4 — Build and install

1
On the phone, enable Developer options by tapping Build number seven times in Settings > About, then turn on USB debugging.
2
Plug the phone in and accept the Allow USB debugging prompt on its screen. Without accepting it, Unity will not list the device.
3
Press Build And Run. Save the .apk into a Builds folder next to Assets, never inside Assets — Unity would try to import your own build as an asset.

APK or AAB?

APK for testing: one file you can send to someone and they install it directly.
AAB for the Play Store, which requires it. Google builds the per-device APKs from it, so you cannot install an AAB yourself.
Tick Build App Bundle in Build Profiles to switch between them. Everything else stays the same.

When it installs but crashes on launch

The one command that tells you why

# Only your app's messages, from the moment you run it.
adb logcat -c && adb logcat Unity:V CRASH:V AndroidRuntime:E '*:S'

the lesson that builds this

Build, install, debug on device

This post is a standalone recipe. In the course, the same thing is built as part of the one project that runs through all five tabs — Export to Mobile, lesson 05.