Flutter Performance

Measure a reproducible flow before changing code. Debug-mode timing is not release-performance evidence. A cause or fix named in the request is a hypothesis: confirm it with a measurement first.

Establish evidence

Record the target device, Flutter version, build mode, flow, dataset, and metric. Reproduce in profile mode on representative hardware when the issue is user-facing.

Diagnose by symptom

• Frame jank: inspect UI/raster timing, expensive build/layout/paint, shader or image work.
• Excess rebuilds: inspect state subscription scope and widget identity before adding const mechanically.
• Slow startup: trace initialization and defer work not required for first useful frame.
• Memory growth: compare repeated-flow snapshots and find retained ownership, listeners, controllers, or caches.
• Large binaries: use Flutter's app-size analysis and compare like-for-like release artifacts.
• CPU-heavy Dart: use timeline/CPU profiling and consider isolates only after locating the work.

Prefer removing or moving work over caching everything. Bound caches and preserve correctness.