How to get APK from Android Studio: from debug to release version

Have you developed an application in Android Studio and now you want to get it ready APK file for installation on a device or publication in Google Play? This process seems simple only at first glance. In practice, novice developers are faced with build errors, problems with signing, or misunderstanding which version of the APK to choose: debug for testing or release for distribution.

In this article we will analyze all the stages - from preparing the project to generating the final APK, including nuances with application signature, file size optimization and elimination of common errors. You will learn how to:

• 🔧 Collect debug.apk in 2 clicks for quick testing
• 🔐 Generate signature key and protect it from loss
• 📦 Compress APK using Android App Bundle (AAB)
• ⚠️ Fix type errors Failed to read key or Missing keystore

All instructions are valid for Android Studio Giraffe (2022.3.1) and newer, but the basic principles also work in older versions. If you use Flutter, React Native or other frameworks, the APK building process will be similar, but with slight differences in the settings.

1. Preparing the project before building the APK

Before generating the APK, make sure that the project is ready to build. Skipping this step often leads to errors like Build failed or Manifest merger failed.

Open your project in Android Studio and follow these steps:

• 📝 Check build.gradle (Module: app):
  • Make sure that minSdkVersion and targetSdkVersion meet the requirements of your application.
  • Example of correct configuration:

    android {
    defaultConfig {
    minSdkVersion 24
    targetSdkVersion 34
    versionCode 1
    versionName "1.0"
    }
    }

• 🔍 Run linter (Analyze → Inspect Code) to find critical errors in the code.
• 📱 Connect a physical device or run emulator for preliminary testing.

⚠️ Attention: If permissions are specified in AndroidManifest.xml that are not declared in the code, the build will fail mistake. For example,<uses-permission>) that are not declared in the code, the build will fail. For example, CAMERA or READ_CONTACTS require an explicit request in runtime for Android 6.0+.

Also check that there is no duplicate resource files (for example, two res no duplicate resource files (for example, two ic_launcher.png with the same name, but in different folders drawable). This is a common cause of build errors.

2. Building the debug version of the APK (for testing)

Debug version of APK is an uncompressed and unsigned file that can only be installed on devices with USB debugging enabled (USB DebuggingIt is suitable for:

• 🧪 Testing functionality on a real device
• 🐞 Finding bugs using Android Profiler
• 🔄 Quick deployment of changes without signature

To assemble debug.apk, do:

1. In the top menu, select Build → Build Bundle(s) / APK(s) → Build APK.
2. Wait for the build to complete (a notification will appear at the bottom APK(s) generated successfully).
3. Click locate in the notification - the folder will open app/build/outputs/apk/debug/where the file is located app-debug.apk.

The finished APK can be immediately transferred to the device via USB or via ADB:

adb install app/build/outputs/apk/debug/app-debug.apk

⚠️ Attention: The Debug version contains debugging information, which increases its size by 30-50% compared to the release. Do not distribute it outside the development team - this violates the rules. Google Play.

3. Generating a release version of an APK (for publication)

Release version of APK is an optimized and signed file that can be uploaded to Google Play, sent to testers or distributed via a website. Unlike debug, it is:

• 🔒 Signed by yours key (keystore)
• 🗜️ Compressed and optimized (debug symbols removed)
• 🚀 Ready for publication in stores

The release-APK generation process consists of two stages: creating a signature key (if it does not exist yet) and assembly with signature.

Step 1: Creating a signature key (keystore)

If you do not have a key yet, do:

1. In Android Studio go to Build → Generate Signed Bundle or APK → APK.
2. Click Create new... and fill in the fields:
   • Key store path — path to the file (for example, C:\keys\my_app.keystore)
   • Password — password for keystore (remember it!)
   • Alias — key name (for example, release_key)
   • Password (for alias) — password for the key (can be the same as the keystore password)
   • Validity (years) — validity period (recommended 25+ years)

Keep the keystore file in a safe place! Losing the key means that you will not be able to update the application on Google Play - you will have to publish it under a new package.

Step 2: Build a signed APK

After creating the key:

1. In the same window, select the created keystore, enter passwords.
2. Specify Build Type: release and Flavor: main (if you do not use custom flavors).
3. Click Finish and wait for the build to complete.

The finished file will be in the folder app/release/ with the name app-release.apk.

What to do if you forgot your keystore password?

Unfortunately, it is impossible to recover your keystore password. data-i="151">Use a backup copy of the keystore (if there is one).

• Use a keystore backup (if available).
• Create a new keystore and publish the application as new (with another package name).

Google Play does not allow updating applications with a new key!

APK type	Signature	Optimization	Size	Purpose
debug.apk	Automatic (Android Studio)	No	Large (+30–50%)	Testing
release.apk	Manual (your keystore)	Yes (ProGuard/R8)	Minimal	Publishing
app-bundle.aab	Manual	Yes (dynamic delivery)	Even less	Google Play

4. APK optimization: ProGuard and size reduction

The Release version of APK by default is optimized through R8 (ProGuard's successor), which:

• 🗑️ Removes unused code (tree shaking)
• 🔤 Shortens class and method names (obfuscation)
• ⚡ Optimizes bytecode

To configure R8, open proguard-rules.pro in the module folder and add rules. For example, to save annotations Retrofit:

-keepattributes Annotation
-keepclassmembers class * {
@retrofit2.http.* <methods>;
}

To further reduce the size:

• 🖼️ Compress images using TinyPNG or WebP-format.
• 📦 Use android:extractNativeLibs="false" in AndroidManifest.xmlif your application does not contain native libraries.
• 🗑️ Remove unnecessary dependencies in build.gradle (check with ./gradlew :app:dependencies).

⚠️ Attention: If after enabling R8 the application stops working, check the build logs for type warnings Note: the configuration refers to the unknown class. This means that R8 has removed the required class - add it to the saving rules (-keep).

5. Typical errors when building APKs and their solutions

Even experienced developers encounter build errors. Here are the most common ones and how to fix them:

If the error persists, try:

1. Update Android Studio and Gradle to the latest versions.
2. Clear cache: File → Invalidate Caches / Restart.
3. Check the build logs in the window Build Output (at the bottom Android Studio).

./gradlew assembleRelease --stacktrace

name: Build APK
on: [push]
jobs:
build:
runs-on: ubuntu-latest
steps:
- uses: actions/checkout@v4
- uses: actions/setup-java@v3
with:
distribution: 'zulu'
java-version: '17'
- run: ./gradlew assembleRelease
- uses: actions/upload-artifact@v3
with:
name: app-release.apk
path: app/build/outputs/apk/release/app-release.apk