Binary size
Measured 2026-10-05 with tools/measure_size.py --platform 36 (Flutter 3.41.9, package:jni 1.0.3, release APK, --target-platform android-arm64, macOS arm64 host). Raw data: size-2026-10-05-android36.json. Uncompressed entry sizes are read from the APK; APK size is the file size.
| Variant | APK bytes | Δ APK vs baseline | libapp.so (Dart AOT) |
libdartjni.so |
classes*.dex |
|---|---|---|---|---|---|
| baseline (no bindings) | 14,426,402 | — | 2,687,920 | 0 | 526,004 |
| bindings imported, unused | 14,776,680 | +350,278 | 2,687,920 | 329,884 | 533,700 |
one API (Context.getPackageName), slice bindings (24 types) |
14,842,216 | +415,814 | 2,753,456 | 329,884 | 533,700 |
| one API, bindings for every android.jar package (6,196 types, 95,888 members, ~1.1M lines) | 14,842,216 | +415,814 | 2,753,456 | 329,884 | 533,700 |
full slice example (examples/flutter/android_slice, UI + all demos) |
15,759,688 | +1,333,286 | 3,670,960 | 329,884 | 533,724 |
Findings#
- Unused generated APIs are not included. The app using one API with bindings generated for the entire SDK is byte-identical in size to the same app with a 24-type slice. With bindings imported but nothing called,
libapp.sois identical to the baseline. - The fixed overhead of the approach comes from
package:jni's native helper (libdartjni.so, 329,884 bytes uncompressed for arm64) and its Java support classes (+7,696 bytes of dex) — not from generated code. - Calling one API added 65,536 bytes to
libapp.so. This equals one 64 KiB segment-alignment step of the AOT snapshot, so the true code delta is not resolvable at this granularity.
React Native (Android)#
Measured 2026-10-05 with tools/measure_rn_size.py --platform 36 (React Native 0.87.1, Hermes, release APK, arm64-v8a). Raw data: size-2026-10-05-rn-android36.json.
| Variant | APK bytes | Δ APK vs baseline | JS bundle (Hermes bytecode) | libappmodules.so |
classes*.dex |
|---|---|---|---|---|---|
baseline (@react-native-community/cli init) |
18,623,666 | — | 1,003,708 | 146,472 | 11,615,424 |
| one API, slice bindings (24 types) | 19,312,390 | +688,724 | 1,456,236 | 468,104 | 11,617,940 |
| one API, bindings for every android.jar package (6,196 types) | 57,776,278 | +39,152,612 | 29,319,676 | 11,060,840 | 11,617,940 |
Findings:
- Unlike Dart, React Native does not remove unused bindings. Metro does not tree-shake and the C++ member tables are looked up by name at runtime, so every generated class ships. With full-SDK bindings the APK grows by 39 MB. Generate only what the app uses (
entries+depth); the slice costs 0.69 MB (runtime + 24 types). - The fixed overhead (runtime + 24 types) is ~452 KB of Hermes bytecode and ~322 KB of native code.
Flutter on iOS (release, device arm64, unsigned)#
Measured 2026-10-05 with tools/measure_ios_size.py (flutter build ios --release --no-codesign, Xcode 27.0 SDK, deployment target 15.0). Raw data: size-startup-2026-10-05-wp7.json. Sizes are of the built Runner.app (an IPA is not produced without signing).
| Variant | Runner.app bytes |
Δ vs baseline | App.framework/App (Dart AOT) |
objective_c.framework |
|---|---|---|---|---|
| baseline (no bindings) | 13,160,396 | — | 2,883,888 | 0 |
one API (UIDevice.systemName), 6-class bindings |
13,463,333 | +302,937 | 2,916,992 | 269,005 |
| one API, bindings for all of Foundation + UIKit | 13,463,317 | +302,921 | 2,916,992 | 268,989 |
full example (examples/flutter/ios_slice, incl. Swift adapters) |
15,039,537 | +1,879,141 | 3,812,080 | 268,813 |
The Dart AOT binary is identical with 6-class bindings and with bindings for all of Foundation + UIKit: unused generated APIs are removed on iOS too. The fixed overhead is package:objective_c's framework (~269 KB) plus 33,104 bytes of AOT code for the call.
Android App Bundle (Flutter, release)#
tools/measure_size.py --aab (all ABIs in the bundle).
| Variant | .aab bytes |
Δ vs baseline | arm64 libapp.so |
arm64 libdartjni.so |
|---|---|---|---|---|
| baseline | 38,041,563 | — | 2,687,920 | 0 |
| bindings imported, unused | 38,227,476 | +185,913 | 2,687,920 | 131,432 |
| one API, slice bindings | 38,334,631 | +293,068 | 2,753,456 | 131,432 |
| one API, bindings for every android.jar package | 38,334,736 | +293,173 | 2,753,456 | 131,432 |
Startup (Android emulator)#
tools/measure_startup.py (am start -W TotalTime, 10 cold starts after one warm-up, API 37 arm64 emulator with software GPU): baseline median 4570.5 ms (range 3373–5406), one API with slice bindings 4793.5 ms (range 3573–5352). The ranges overlap almost entirely; this emulator cannot resolve a startup difference. Bindings do no work at startup (lazy class/method IDs).
Not measured yet#
Physical devices (none measured without consent), iOS startup, React Native iOS size.
docs/benchmarks/size.md