A Look Behind the Scenes of React & Optimization TechniquesEntry 2 of 10

Profiling with React DevTools

The React DevTools browser extension includes a Profiler that records which components rendered, how long they took, and why.

Notes

  1. Install React DevTools for Chrome or Firefox.
  2. Open the Profiler tab, click record, interact with the app, and stop recording.
  3. The flame graph shows every component that rendered. Enable "Record why each component rendered" in the settings to see the cause (state, props, context, or parent).

Measure first, then optimize. Guessing leads to memo() and useMemo in places where they cost more than they save.

Angular

Angular DevTools has a Profiler tab that records change detection cycles and shows time spent per component. Its Injector Tree and signal graph views help trace where updates come from.

Quick reference

ReactAngular
React DevTools → ProfilerAngular DevTools → Profiler
"Why did this render?" settingChange detection cycle breakdown