React Rendering Performance

Skill Resources

• Activation and cross-agent notes: references/activation.md
• Use ultrathink or the deepest available reasoning mode before changing architecture, security, migration, or performance-critical paths.
• Template: templates/profiler-session.md

Performance work without measurement is guessing. The correct sequence: measure with the Profiler, identify the bottleneck type, then apply the right tool. Memoizing everything is not a strategy.

React 19 Compiler: What Changed

React Compiler (stable in React 19) automatically memoizes components, values, and callbacks. It analyzes the component tree statically and inserts useMemo, useCallback, and React.memo where they would help — without you writing them.

What the Compiler Handles Automatically