Frequently asked questions

• Which performance dashboards have metrics that are related to Flutter?
  • https://flutter-dashboard.appspot.com/
  • https://flutter-flutter-perf.skia.org/t/?subset=regressions
  • https://flutter-engine-perf.skia.org/t/?subset=regressions
  • https://flutter-dashboard.appspot.com/benchmarks.html (to be retired)
• How do I add a benchmark to Flutter?
  • How to write a render speed test for Flutter
  • How to write a memory test for Flutter
• What are some tools for capturing and analyzing performance metrics?
  • Dart DevTools
  • Apple instruments
  • Linux perf
  • [Chrome tracing (enter about:tracing in your Chrome URL field)][tracing]
  • Android systrace (adb systrace)
  • Fuchsia fx traceutil
  • https://ui.perfetto.dev/
  • https://www.speedscope.app/
• My Flutter app looks janky or stutters. How do I fix it?
  • Improving rendering performance
• What are some costly performance operations that I need to be careful with?
  • Opacity, Clip.antiAliasWithSaveLayer, or anything that triggers saveLayer
  • ImageFilter
  • Also see Performance best practices
• How do I tell which widgets in my Flutter app are rebuilt in each frame?
  • Set debugProfileBuildsEnabled true in widgets/debug.dart.
  • Alternatively, change the performRebuild function in widgets/framework.dart to ignore debugProfileBuildsEnabled and always call Timeline.startSync(...)/finish.
  • If you use IntelliJ, a GUI view of this data is available. Select show widget rebuild information, and you will see which widgets rebuild visually in your IDE.
• How do I query the target frames per second (of the display)?
  • Get the display refresh rate
• How to solve my app’s poor animations caused by an expensive Dart async function call that is blocking the UI thread?
  • Spawn another isolate using the compute property
• How do I determine my Flutter app’s package size that will be downloaded by a user?
  • See Measuring your app’s size
• How do I see the breakdown of the Flutter engine size?
  • Visit the binary size dashboard, and replace the git hash in the URL with a recent commit hash from GitHub commits.
• How can I take a screenshot of an app that is running and export it as a SKP file?
  • Run flutter screenshot --type=skia --observatory-uri=...
  • Known issue of a SKP screenshot:
    • Doesn’t record images in real devices Issue 21237
  • To analyze and visualize the SKP file, visit https://debugger.skia.org/.
• How do I retrieve the shader persistent cache from a device?
  • On Android, you can do the following:

    adb shell
    run-as <com.your_app_package_name>
    cp <your_folder> <some_public_folder, e.g., /sdcard> -r
    adb pull <some_public_folder/your_folder>
    

• How do I perform a trace in Fuchsia?
  • See Fuchsia tracing guidelines

[tracing]: https://www.chromium.org/developers/how-tos/trace-event-profiling-tool