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Troubleshooting & FAQ for Unity and Firebase

This page offers tips and troubleshooting for Unity-specific issues that you might encounter when using Firebase.

Have other challenges or don't see your issue outlined below? Make sure to check out the main Firebase FAQ for more pan-Firebase or product-specific FAQ.

An issue with single dex while building Android app

While building Android app, you may encounter a build failure related to having a single dex file. The error message looks similar to the following, if your project is configured to use the Gradle build system.

Cannot fit requested classes in a single dex file.

Dalvik Executable (.dex) files are used to hold a set of class definitions and their associated adjunct data for Android applications (.apk). A single dex file is limited to reference to 65,536 methods. The build will fail if the total number of methods from all Android libraries in your project exceeds this limit.

Unity introduced Minification in 2017.2, which uses Proguard (or other tools in some versions of Unity) to strip out unused code, which can reduce the total number of referenced methods in a single dex file. The option can be found in Player Settings > Android > Publishing Settings > Minify. The options may differ in different version of Unity so refer to the official Unity documentation.

If the number of referenced methods still exceeds the limit, another option is to enable multidex. There are multiple ways to achieve this in Unity:

More details can be found in the multidex user guide.

Issues when building for Android with minSdkVersion 23

When building for Android, if you target minSdkVersion 23, it might fail on the dexing step, usually in the Gradle task ':launcher:mergeExtDexDebug', where it will say it "Failed to transform" one of the Android libraries. This is caused because of a bug in the default dex tool in the Android SDK that most Unity editors use, and can be fixed in a few different ways:

buildscript {
  repositories {
    mavenLocal()
    maven { url 'https://maven.google.com'  }
    mavenCentral()
  }
  dependencies {
    classpath 'com.android.tools:r8:8.3.37'
  }
}

Issues when building for iOS with Cocoapods

When building for iOS, Cocoapod installation may fail with an error about the language locale, or UTF-8 encoding. There are currently several different ways to work around the issue.

How to update the version of Firebase Unity SDKs

The process to update the versions of Firebase Unity SDKs depends on how they were initially imported. Here are the two alternative import methods:

In your Unity project, you should only use one import method to manage all your Firebase packages. The instructions below can be used to not only update the version of individual packages, but also, if needed, to migrate package management to UPM (the recommended import method).

Packages imported as .unitypackage files into the Assets/ directory

If Firebase packages are in the Assets/ directory, you have two options for updating the SDK version: