DEX code optimization

DEX code optimization is an Android vitals finding that helps you monitor and improve your app's compilation quality, size, and performance. Optimizing and obfuscating your code using R8 or alternative tools (such as ProGuard-compatible optimizers or secondary DEX post-processors) reduces your app's DEX size, improves runtime performance, and minimizes its memory footprint.

DEX, or Dalvik Executable, files contain the compiled code used to run your app. This typically includes Java and Kotlin code, as opposed to compiled C++ code or .so files.

Android vitals reports DEX code optimization metrics for all apps and games, but only enforces thresholds for apps and games that meet specific size requirements.

Detect the problem

Android vitals can alert you in Play Console when your app's DEX code optimization, shrinking, or obfuscation levels don't meet the minimum defined percentages.

How optimization scores are calculated

For apps built with the latest patch version of AGP 8.10 or higher (for example, 8.10.1 rather than 8.10.0), these percentages are pulled from the included r8.json file. Make sure you use the latest patch version of AGP and R8 for your minor version so that accurate metadata is generated.

For apps built with earlier versions of AGP, or apps optimized with an alternative code optimizer where r8.json isn't included, Android vitals estimates obfuscation percentages as a proxy using the mapping.txt file (if included) or DEX heuristics.

Total DEX size minimums

While Android vitals calculates code optimization metrics for all apps, you will only receive alerts if your app bundle meets the following total DEX size requirements:

  • Apps: Bundle contains at least 10 MB of DEX code measured as uncompressed size
  • Games: Bundle contains at least 50 MB of DEX code measured as uncompressed size

Measure code optimization locally

To measure your app bundle's uncompressed DEX size and get the optimization, shrinking, and obfuscation percentages that match the findings in Android vitals, run android analyze:

android analyze <yourapp>.aab

Fix the problem

To address low DEX code optimization scores, review the recommendations based on your build system and optimizer:

R8

To improve your R8 DEX code optimization scores, see the guidance at Improve R8 optimization, and use the R8 Configuration Analyzer to understand how your keep rules affect your optimization, shrinking, and obfuscation scores (for detailed definitions of these metrics, see Understand the report).

If you use the Android Gradle Plugin (AGP), you can also use the R8 Analyzer skill to get additional guidance on optimizing your app's keep rules. If you use Bazel, you also have access to the R8 Configuration Analyzer; see the rules_android R8 optimization documentation.

Non-R8 optimizers and DEX post-processors

If your build pipeline uses custom build tools or secondary DEX post-processors, take the following steps to improve your app's optimization:

  • Open your app bundle in Android Studio and view it in the APK Analyzer.
  • Select all of the .dex files.
  • Pay close attention to the files with the largest size as you toggle the "Deobfuscate names" button (note: this requires you to load a mapping.txt file). If you find some of those files stay large while obfuscated, it's likely they're affected by package-wide keep rules.
  • Look either in your proguard-rules.pro file, configuration.txt, or the equivalent for your optimizer if you're not using R8, and search for keep rules that match the packages that aren't getting obfuscated. For example, if com.foo. is a large package in your DEX files, look for keep rules of the format -keep com.foo.** or -keep com.foo.bar.**.
  • Keep in mind that library consumer keep rules might not be as straightforward to identify. If you suspect a library consumer rule is impacting optimization, you can inspect the library directly using android analyze <library>.aar, or validate it by adding the library to a standalone sample app using a recent version of AGP and inspecting it with the R8 Configuration Analyzer.