# Performance FAQ > Frequently asked questions about Flutter performance This page collects some frequently asked questions about evaluating and debugging Flutter's performance. * Which performance dashboards have metrics that are related to Flutter? * [Flutter dashboard on appspot][] * [Flutter Skia dashboard][] * [Flutter Engine Skia dashboard][] [Flutter dashboard on appspot]: https://flutter-dashboard.appspot.com/ [Flutter engine Skia dashboard]: https://flutter-engine-perf.skia.org/t/?subset=regressions [Flutter Skia dashboard]: https://flutter-flutter-perf.skia.org/t/?subset=regressions * How do I add a benchmark to Flutter? * [How to write a render speed test for Flutter][speed-test] * [How to write a memory test for Flutter][memory-test] [memory-test]: https://github.com/flutter/flutter/blob/main/docs/contributing/testing/How-to-write-a-memory-test-for-Flutter.md [speed-test]: https://github.com/flutter/flutter/blob/main/docs/contributing/testing/How-to-write-a-render-speed-test-for-Flutter.md * What are some tools for capturing and analyzing performance metrics? * [Dart/Flutter DevTools](/tools/devtools) * [Apple instruments](https://en.wikipedia.org/wiki/Instruments_(software)) * [Linux perf](https://en.wikipedia.org/wiki/Perf_(Linux)) * [Chrome tracing (enter `about:tracing` in your Chrome URL field)][tracing] * [Android systrace (`adb systrace`)][systrace] * [Fuchsia `fx traceutil`][traceutil] * [Perfetto](https://ui.perfetto.dev/) * [speedscope](https://www.speedscope.app/) [systrace]: https://developer.android.com/studio/profile/systrace [tracing]: https://www.chromium.org/developers/how-tos/trace-event-profiling-tool [traceutil]: https://fuchsia.dev/fuchsia-src/development/tracing/usage-guide * My Flutter app looks janky or stutters. How do I fix it? * [Improving rendering performance][] [Improving rendering performance]: /perf/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][] [`Clip.antiAliasWithSaveLayer`]: https://api.flutter.dev/flutter/dart-ui/Clip.html#antiAliasWithSaveLayer [`ImageFilter`]: https://api.flutter.dev/flutter/dart-ui/ImageFilter-class.html [`Opacity`]: https://api.flutter.dev/flutter/widgets/Opacity-class.html [Performance best practices]: /perf/best-practices [`savelayer`]: https://api.flutter.dev/flutter/dart-ui/Canvas/saveLayer.html * How do I tell which widgets in my Flutter app are rebuilt in each frame? * Set [`debugProfileBuildsEnabled`][] true in [widgets/debug.dart][debug.dart]. * Alternatively, change the `performRebuild` function in [widgets/framework.dart][framework.dart] to ignore `debugProfileBuildsEnabled` and always call `Timeline.startSync(...)/finish`. * If you use IntelliJ, a GUI view of this data is available. Select **Track widget rebuilds**, and your IDE displays which the widgets rebuild. [`debugProfileBuildsEnabled`]: https://api.flutter.dev/flutter/widgets/debugProfileBuildsEnabled.html [debug.dart]: https://github.com/flutter/flutter/blob/main/packages/flutter/lib/src/widgets/debug.dart [framework.dart]: https://github.com/flutter/flutter/blob/main/packages/flutter/lib/src/widgets/framework.dart * How do I query the target frames per second (of the display)? * [Get the display refresh rate][] [Get the display refresh rate]: https://github.com/flutter/flutter/blob/main/docs/engine/Engine-specific-Service-Protocol-extensions.md#get-the-display-refresh-rate-_fluttergetdisplayrefreshrate * 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()`][] method, as demonstrated in [Parse JSON in the background][] cookbook. [`compute()`]: https://api.flutter.dev/flutter/foundation/compute-constant.html [Parse JSON in the background]: /cookbook/networking/background-parsing * How do I determine my Flutter app's package size that a user will download? * See [Measuring your app's size][] [Measuring your app's size]: /perf/app-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 [Flutter's GitHub commits][]. [binary size dashboard]: https://storage.googleapis.com/flutter_infra_release/flutter/241c87ad800beeab545ab867354d4683d5bfb6ce/android-arm-release/sizes/index.html [Flutter's GitHub commits]: https://github.com/flutter/flutter/commits/main * 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=...` * Note a known issue viewing screenshots: * [Issue 21237][]: Doesn't record images in real devices. * To analyze and visualize the SKP file, check out the [Skia WASM debugger][]. [Issue 21237]: https://github.com/flutter/flutter/issues/21237 [Skia WASM debugger]: https://debugger.skia.org/ * How do I retrieve the shader persistent cache from a device? * On Android, you can do the following: ```console adb shell run-as cp -r adb pull ``` * How do I perform a trace in Fuchsia? * See [Fuchsia tracing guidelines][traceutil]