Build, install, debug on device

your project so far

Assets/

Scripts/

MobileBoot.csSaveSystem.csScreenLogger.cs

Settings/

URP mobile asset

Builds/

signed .apk / .aab

Project settings

keystore

you already havethis lesson adds

Everything is configured and the Knight can save its progress. Now press the button, get the file onto a phone, and learn to read the logs when it misbehaves.

animated diagram

Scenes and assets go in, an installable package comes out.

Build and Run

1
File▸Build Profiles▸Android. Tick Development Build while you are still testing.
2
With the phone plugged in, press Build And Run. Unity builds, installs and launches in one step.
3
Save the output as Builds/game-dev.apk. Never inside Assets/ — Unity would try to import your own build.
4
First build: 10–20 minutes. Later builds with the same settings: 1–3 minutes.

Signing — the part everyone forgets

A debug build is signed with a temporary key. A release build needs your own keystore, and without it you cannot sign an update. Google Play can reset a lost upload key, but only through a support request that takes days — most other stores cannot help at all.

1
Project Settings▸Player▸Publishing Settings▸Keystore Manager▸Create New.
2
Save it OUTSIDE the project folder and back it up in two places. Treat this file as irreplaceable.
3
Never commit the .keystore or its passwords to git. Put *.keystore in .gitignore right now.
4
For the store: untick Development Build, tick Build App Bundle (Google Play), then Build.

Installing manually with adb

terminal

# install, replacing an existing copy
adb install -r Builds/game-dev.apk

# uninstall when the signature changed
adb uninstall com.yourstudio.yourgame

# launch it without touching the phone
adb shell monkey -p com.yourstudio.yourgame 1

# copy a build to the phone's Downloads folder
adb push Builds/game-dev.apk /sdcard/Download/

Reading the device log

When the game crashes on the phone but works in the editor, logcat is the only thing that will tell you why.

terminal

# only Unity's messages — this is the one you want
adb logcat -s Unity

# clear the old log first so you only see this run
adb logcat -c && adb logcat -s Unity

# save it to a file to read carefully
adb logcat -s Unity > crash.txt

Every Debug.Log you wrote appears here, on the real device, in real time.
Look for lines starting with NullReferenceException — the stack trace below it names the exact script and line.
A crash with no Unity message at all is usually native: out of memory, or a missing ARM64 library.

An on-screen log for testers without a cable

ScreenLogger.cs

using System.Collections.Generic;
using UnityEngine;

public class ScreenLogger : MonoBehaviour
{
    private readonly List<string> lines = new List<string>();
    [SerializeField] private int maxLines = 14;

    void OnEnable()  => Application.logMessageReceived += Handle;
    void OnDisable() => Application.logMessageReceived -= Handle;

    void Handle(string message, string stack, LogType type)
    {
        lines.Add($"[{type}] {message}");
        if (lines.Count > maxLines) lines.RemoveAt(0);
    }

    void OnGUI()
    {
        GUI.skin.label.fontSize = 26;
        GUI.Label(new Rect(20, 20, Screen.width - 40, Screen.height - 40),
                  string.Join("\n", lines));
    }
}

Before you upload to the store

Untick Development Build — a dev build is slower and cannot be published.
Test on at least one low-end device. The reviews you get are written on cheap phones.
Check the app on a phone with a notch and on a tablet — that is where UI anchoring bugs show up.
Play Console requires: an AAB, a target API level no more than a year old, a privacy policy URL, and a 512×512 icon.