React 18 fully supports class components and enables incremental migration—you don't need to convert everything to hooks immediately. For small apps with dozens of components using legacy React 17 patterns, you can upgrade to React 18 in 1-2 weeks using automated tooling and phased validation, then gradually convert components to functional patterns at your own pace. The key insight: automatic batching, concurrent features, and improved performance work with class components out of the box.
Why it matters: React 18 brings automatic batching (fewer re-renders), concurrent rendering foundations, better SSR with Suspense, and future-proofing—all while maintaining full backward compatibility. Migration effort is low to medium for well-maintained codebases, higher for legacy code using UNSAFE_ lifecycle methods without proper cleanup.
Backstory: Released March 2022, React 18 represents the biggest architectural shift in React's history wi