Summary

React Conf 2021 introduced the React 18 release candidate and outlined a multi-platform vision for React, including concurrent features, improved Suspense semantics, streaming server rendering, new hooks, and updates to developer tooling. The conference (streamed and translated) made all talks available and emphasized a gradual-adoption strategy so teams can opt in to concurrent features without large rewrites.

Key Points

• React 18 RC is available now; this RC is expected to be the same build shipped as stable pending feedback. Install with npm install react@rc react-dom@rc and test before upgrading production.
• New root API: replace ReactDOM.render(...) with const root = ReactDOM.createRoot(container); root.render(<App />); to opt into the new renderer.
• Concurrent features (no separate "concurrent mode") let apps adopt features incrementally; no major breaking changes required for upgrade.
• Suspense and streaming SSR: Suspense boundaries can be streamed independently so users see and interact with content faster on the first load.
• New/updated hooks: useId, useSyncExternalStore, and useInsertionEffect were defined to support libraries and concurrent rendering.
• Tooling and workflow: a new React DevTools team and Timeline Profiler were announced to help debug concurrent behavior and performance.
• Community & resources: recordings of all 19 talks (keynotes and deep dives) are available for migration guidance, demos, and implementation details.

Practical next steps for engineers

• Try the RC in a branch or staging environment: npm install react@rc react-dom@rc and switch to createRoot.
• Audit third-party libraries for compatibility with useSyncExternalStore and concurrent rendering semantics.
• Learn Suspense-driven SSR patterns to incrementally stream UI and improve time-to-interactive.
• Watch the React Conf talks relevant to migration (keynotes, SSR, DevTools, and working group sessions) for concrete examples and demos.