Reducing React Native App Size with Spotify Ruler & ProGuard

One of the most important aspects of building a mobile app is ensuring that the final packaged application is lightweight, efficient, and optimized for distribution. Large app sizes can negatively affect user acquisition, as potential users are often discouraged from downloading apps that take up significant storage space. Moreover, smaller apps typically load faster, consume fewer resources, and provide an overall smoother user experience.

Before diving into the technical implementation, let’s quickly touch upon why app size optimization is critical:

The first step in optimizing app size is measurement. Without visibility into what contributes to the app’s bulk, it is nearly impossible to optimize effectively. This is where the Spotify Ruler Gradle plugin comes into play.

The Ruler plugin provides insights into your APK or AAB (Android App Bundle) size. It breaks down the contribution of Java bytecode, resources, assets, and even external libraries. By using this tool, you can identify exactly which modules or dependencies are consuming unnecessary space.

Then, apply the plugin in your android/app/build.gradle:

This ensures that when you build your release version, ProGuard minifies the code and strips away any unused logic, resulting in a smaller build.

Another contributor to app size is unused resources such as images, layouts, and XML files. Android provides a resource shrinker that works hand-in-hand with ProGuard to remove unused resources from your final build.

Here’s what each line does:

You can further customize Ruler to simulate different runtime environments. Add the following configuration at the end of your android/app/build.gradle:

Here’s what these parameters mean:

Once you’ve set up the Ruler plugin and Gradle configurations, you can generate a size report for your release bundle. Navigate to the android folder of your project and run:

This command generates a detailed report highlighting the size contribution of different modules, libraries, and resources. With this report, you can identify heavy dependencies or unused assets and take corrective measures. Below is the evidence which showcases the difference in install and download size with a detailed breakdown of the components.

According to the official Spotify Ruler GitHub documentation, the plugin provides:

While ProGuard, resource shrinking, and Ruler form the backbone of optimization, here are some additional strategies you can adopt:

Reducing app size is not just a technical exercise—it directly impacts business outcomes:

Optimizing app size in React Native is an iterative process that involves analysis, configuration, and continuous monitoring. By using tools like the Spotify Ruler plugin, enabling ProGuard, shrinking resources, and following best practices, you can significantly reduce both the download and install sizes of your app.

The key takeaway is that app size optimization is not just about technical performance—it also drives business value by improving user experience, increasing adoption rates, and lowering churn.