How I Reduced the Size of My React Native App by 85%

How and Why You Should Do It

I borrowed 25$ from my friend to start a Play Store Developer account to put up my first app. I had already created the app, created the assets and published it in the store.

Nobody wants to download a todo list app that costs 25mb of bandwidth and another 25 MB of storage space.

So today I am going to share with you how I reduced the size of Tet from 25 MB to around 3.5 MB.

Size Matters

Like any beginner, I wrote my app using Expo, the awesome React Native platform that makes creating native apps a breeze. There is no native setup, you write javascript and Expo builds the binaries for you.

I love everything about Expo except the size of the binaries. Each binary weighs around 25 MB regardless of your app.

So the first thing I did was to migrate my existing Expo app to React Native.

Migrating to React Native

• react-native init a new project with the same name
• Copy the source files over from Expo project
• Install all dependencies of the Expo project except Expo specific libraries.
• Make neccesary adjustments to app.json file
• Copy over your .git folder into the new project.
• Download the signing key of your Android app from Expo using exp fetch:android:keystore and set it up
• Build and test your app

This reduces the size to around 7.5 MB, thin but we can go thinner.

Reducing size of React Native App (Android)

This is what you have been waiting for, I know.

• Open up android/app/build.gradle
• Set def enableProguardInReleaseBuilds = true this would enable Progaurd to compress the Java Bytecode. This reduces the app size by a tad bit
• Set def enableSeparateBuildPerCPUArchitecture = true . Android devices support two major device artitectures armebi and x86. By default RN builds the native librariers for both these artitectures into the same .apk.

Setting the last function creates two distinct .apk in the build folder. You have to upload both of this .apk to Play Store and Google would take care of distributing the app to the correct architectures.

Using this split generates version numbers for both .apks in the order of 104856 and such. This is auto-generated by the build to avoid version conflicts, so don’t freak out (I did).

This split reduced the .apk size from around 7MB to 3.5MB for arm and 5MB for x86 respectively.

Yeah

So that’s how you lose weight. Reducing the size of your app has many added benefits, the best being more users will be willing to download your app.