Flutter 16 KB Page Size: We Measured Three Flutter Versions

From February 1, 2027, Google Play will not release updates of apps that target Android 15 or higher unless they support 16 KB memory pages on 64-bit devices. We created a fresh app with each of three Flutter versions and measured both the files it builds and the APKs made from its AAB. The Flutter engine and the compiled Dart code were aligned on all three, and every release APK Flutter built passed. The AABs of the two older versions did not: in the APKs built from them, the libraries started at 4 KB-aligned offsets rather than 16 KB, because those projects use an Android Gradle Plugin older than 8.5.1. A plugin that ships its own native library is the other risk.

What we measured

Method, October 3, 2026: in the Flutter builder images Code2Native runs, flutter create with default settings, then flutter build apk --release and flutter build appbundle --release. We read the program headers of every 64-bit library (arm64-v8a and x86_64) in the APK and the AAB, the same check our website builds run before they are marked ready for Google Play, and ran zipalign -c -P 16 -v 4 from Android build-tools 36.0.0 on each APK. Sizes are in decimal megabytes; Flutter 3.19.6's own build output prints them in binary units.

The AAB: the APKs Google Play builds from it

Google Play does not install your AAB. It builds APKs from it with bundletool, following the packaging settings inside the bundle, and those settings come from your project's Android Gradle Plugin.

Method: we read each bundle's settings with bundletool dump config, ran bundletool build-apks (version 1.18.3) for a 64-bit (arm64-v8a) Android 15 phone, and read where each library starts in the APK it built. Google's guide is explicit about why that matters: “16 KB devices require apps that ship with uncompressed shared libraries to align them on a 16 KB zip-aligned boundary.”

What the numbers mean

• Flutter's own libraries are fine. Both were aligned to 64 KB, four times what 16 KB pages need, on every version we built.
• A new project packs the APK differently. A fresh 3.44.5 project stores the libraries uncompressed at 16 KB boundaries, so Android can load them straight from the APK: its 42.8 MB of libraries fill almost the whole 43.4 MB APK. The two older projects compress about 39.5 MB of libraries to 18 MB, and Android unpacks them at install. Both ways pass.
• The AAB depends on your Android Gradle Plugin. The 3.24.5 and 3.19.6 bundles ask for uncompressed libraries without saying how to align them, so the APKs built from them fail even though the APKs Flutter built directly pass. Flutter does not raise the plugin for you: the version stays in your own Gradle files, usually android/settings.gradle or settings.gradle.kts (older projects set it in android/build.gradle). Flutter 3.35 to 3.41 refuse only plugins below 8.1.1, so a project raised just enough to build there still makes this kind of bundle; Flutter 3.44.5 requires 8.6.0 or later.
• The Flutter version still matters for Google Play. By default, Flutter 3.24.5 and 3.19.6 target API 34 and 33, below what Play accepts for updates. See Flutter target API 36.
• Plugins are the other risk. A fresh app has no plugins. A plugin that ships a prebuilt .so brings its own alignment, and Google warns that some SDK prebuilts are not 16 KB compatible.

Check your own build

Run Google's check on the release APK:

zipalign -c -P 16 -v 4 app-release.apk

Then open the APK in Android Studio (Build > Analyze APK), expand lib, and read the Alignment column for every 64-bit .so. A failing library's file name usually points to the plugin or SDK that ships it. The -P option needs build-tools 35.0.0 or later, and zipalign marks a compressed library “OK - compressed” without checking it, so for compressed libraries the Alignment column is the check that counts.

For an AAB, read the packaging it asks Google Play for:

bundletool dump config --bundle=app-release.aab

If uncompressNativeLibraries shows "enabled": true, it also needs "alignment": "PAGE_ALIGNMENT_16K". If it is missing, upgrade the Android Gradle Plugin to 8.5.1 or later (8.6.0 or later on Flutter 3.44.5), with the Gradle version it needs. If you can't, Google's alternative is to have Gradle compress the libraries, in android/app/build.gradle:

android {
    packagingOptions {
        jniLibs {
            useLegacyPackaging true
        }
    }
}

In build.gradle.kts, the line is useLegacyPackaging = true. With plugin 8.0 or older, also add android.bundle.enableUncompressedNativeLibs=false to android/gradle.properties. Compressed libraries take more space once the app is installed. Google's 16 KB page size guide adds the build-side rules: native code built with NDK r28 or later is aligned by default, older NDKs need linker flags, and Android Gradle Plugin 8.5.1 or later aligns uncompressed libraries.

Building it in the cloud

Code2Native's source builds use Flutter 3.44.5 by default and build the APK or AAB you choose. Every Android build from source checks the file you get, each 64-bit library and, for an AAB, the packaging it asks Google Play for. The build log names what fails (libraries by file name, the first five, then a count) and how to fix it. The check never stops a build. Source builds need Builder ($39/month) or Pro; check that your project is supported before you buy.