How to Sign Flutter App for Android and iOS

To sign a Flutter app, you must create a signing key and configure your app to use it. For Android, set up a key.properties file and update build.gradle. For iOS, use Xcode to manage signing certificates and provisioning profiles.

Syntax

Signing a Flutter app involves configuring platform-specific files:

• Android: Use key.properties to store key info and update android/app/build.gradle to use the signing config.
• iOS: Use Xcode to select a signing certificate and provisioning profile in the project settings.

groovy

android {
    signingConfigs {
        release {
            keyAlias keystoreProperties['keyAlias']
            keyPassword keystoreProperties['keyPassword']
            storeFile file(keystoreProperties['storeFile'])
            storePassword keystoreProperties['storePassword']
        }
    }
    buildTypes {
        release {
            signingConfig signingConfigs.release
        }
    }
}

Example

This example shows how to sign an Android Flutter app by creating a key.properties file and configuring build.gradle.

groovy

1. Create <code>key.properties</code> in <code>android/</code> folder with content:
storePassword=myStorePassword
keyPassword=myKeyPassword
keyAlias=myKeyAlias
storeFile=my-release-key.jks

2. Update <code>android/app/build.gradle</code>:

// Load properties
Properties keystoreProperties = new Properties()
File keystorePropertiesFile = rootProject.file('key.properties')
if (keystorePropertiesFile.exists()) {
    keystoreProperties.load(new FileInputStream(keystorePropertiesFile))
}

android {
    signingConfigs {
        release {
            keyAlias keystoreProperties['keyAlias']
            keyPassword keystoreProperties['keyPassword']
            storeFile file(keystoreProperties['storeFile'])
            storePassword keystoreProperties['storePassword']
        }
    }
    buildTypes {
        release {
            signingConfig signingConfigs.release
            minifyEnabled false
            shrinkResources false
        }
    }
}

Output

Flutter app builds with release signing using the specified keystore.

Common Pitfalls

Common mistakes when signing Flutter apps include:

• Not creating or referencing the key.properties file correctly for Android.
• Using incorrect passwords or aliases in the signing config.
• For iOS, forgetting to select the correct signing team or provisioning profile in Xcode.
• Not cleaning the build after changing signing configs, causing stale builds.

groovy

Wrong way (missing key.properties):
android {
    signingConfigs {
        release {
            keyAlias 'myKeyAlias'
            keyPassword 'wrongPassword'
            storeFile file('wrong-path.jks')
            storePassword 'wrongStorePassword'
        }
    }
}

Right way (using key.properties):
Properties keystoreProperties = new Properties()
File keystorePropertiesFile = rootProject.file('key.properties')
if (keystorePropertiesFile.exists()) {
    keystoreProperties.load(new FileInputStream(keystorePropertiesFile))
}

android {
    signingConfigs {
        release {
            keyAlias keystoreProperties['keyAlias']
            keyPassword keystoreProperties['keyPassword']
            storeFile file(keystoreProperties['storeFile'])
            storePassword keystoreProperties['storePassword']
        }
    }
}

Quick Reference

Android Signing Steps:

• Create a keystore with keytool.
• Make key.properties with passwords and alias.
• Update build.gradle to use signing config.
• Build release APK or AAB with flutter build apk --release.

iOS Signing Steps:

• Open ios/Runner.xcworkspace in Xcode.
• Set your team and signing certificate in project settings.
• Ensure provisioning profiles are valid.
• Build archive and export for App Store or TestFlight.

Key Takeaways

Always create and reference a key.properties file for Android signing.

Use Xcode to manage iOS signing certificates and provisioning profiles.

Double-check passwords and file paths to avoid build errors.

Clean your build folder after changing signing configurations.

Test your signed app on devices before publishing.