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Developer 6 min read Published Updated Credibility 86/100

Framework Briefing — React 18 General Availability

React 18’s March 29, 2022 release introduces concurrent rendering, automatic batching, and new data-fetching APIs that require front-end leaders to plan upgrades, testing, and sourcing strategies to capture performance gains without destabilizing production.

Zeph Tech Research Lead

Research lead, Zeph Tech

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Executive briefing: React 18 became generally available on March 29, 2022, delivering concurrent rendering, automatic batching, new hooks such as useId, and the startTransition API to help developers build responsive user interfaces. The release also formalizes streaming server rendering with renderToPipeableStream/renderToReadableStream, integrates with Suspense for selective hydration, and introduces an updated Strict Mode that prepares applications for future concurrent features. Engineering leaders must evaluate how the new APIs change render timing, testing, and performance, and coordinate cross-functional governance to manage risk when migrating production applications.

Assess the implications of concurrent rendering

Concurrent rendering allows React to prepare multiple versions of the UI simultaneously, pausing or aborting rendering work that is no longer needed. Unlike previous synchronous rendering, concurrent mode enables the scheduler to prioritize urgent updates (such as typing) over less critical work. Existing apps opt in by switching to the new createRoot API. Teams should audit codebases for assumptions about synchronous rendering order, side effects, and layout measurements. Components that trigger layout thrashing or rely on immediately updated refs may behave differently when work is interrupted. Testing suites must include scenarios that simulate preemption, such as artificially slowing network requests or using the React Testing Library’s act helpers with concurrent features enabled.

Concurrent rendering does not change React’s semantics for rendering pure components, but any side effects inside render functions or reliance on useEffect ordering should be reviewed. Strict Mode in React 18 intentionally double-invokes certain lifecycle methods in development to surface unsafe patterns. Engineering leaders should enforce lint rules (eslint-plugin-react-hooks) and code review checklists to ensure hooks are used correctly, dependencies arrays are complete, and state updates remain pure.

Operational priorities for migration

Create a phased migration roadmap. Begin with upgrading project dependencies to React 18 and React DOM 18, ensuring accompanying libraries (React Router, Next.js, Material UI) support the new version. Use feature toggles to activate createRoot incrementally per application or micro-frontend. Document regression testing plans that cover interactions, animations, and forms under load. QA teams should employ automated tests (Cypress, Playwright) and performance profilers (React Profiler, Chrome DevTools) to compare render times before and after the upgrade.

Adopt the new automatic batching behavior. In previous versions, React batched state updates only inside event handlers. React 18 extends batching to asynchronous contexts such as promises, setTimeout, and native event handlers. Audit components where developers relied on microtask flushing (e.g., await setState patterns) or where multiple state updates were expected to flush individually. Update documentation and training materials to clarify that state updates may be deferred until the end of the tick. Provide patterns for forcing synchronous updates using flushSync only when necessary, and ensure instrumentation captures any associated performance costs.

Leverage startTransition to mark non-urgent updates. Product teams should identify interactions where background updates—such as search results, filter panels, or analytics dashboards—can be deprioritized to keep the UI responsive. Implement loading indicators via Suspense boundaries to communicate transitional states to users. Define UX guidelines for when to display spinners, skeletons, or stale-while-refreshing views. Collaborate with design teams to test the perceived performance improvements and adjust fallback components accordingly.

Server-side rendering and streaming strategy

React 18 modernizes server rendering with streaming APIs. renderToPipeableStream (Node.js) and renderToReadableStream (web streams) let servers send HTML in chunks, allowing the browser to progressively render content while the server fetches additional data. Teams using Next.js, Remix, or custom server frameworks should evaluate support for these streaming APIs and plan upgrades. Implement Suspense boundaries around data-fetching components so that server-rendered streams can send placeholders while awaiting data. Integrate with edge rendering platforms (Vercel Edge Functions, Cloudflare Workers) to minimize latency.

Selective hydration allows React to prioritize interactive components within server-rendered pages. Audit pages with complex interactive widgets and ensure hydration boundaries are appropriately defined to avoid blocking the main thread. Adopt resource preloading strategies (<link rel="preload">, useId for deterministic IDs) to minimize layout shifts when components hydrate out of order. Work with DevOps teams to benchmark time-to-first-byte (TTFB) and largest contentful paint (LCP) metrics before and after streaming adoption.

Governance and quality assurance

Front-end guilds or architecture councils should update engineering standards to reflect React 18 best practices. Document guidelines on avoiding mutable shared state, handling Suspense fallbacks, and structuring data-fetching logic. Ensure design systems align with concurrent rendering by verifying that component libraries avoid side effects during rendering and support Suspense for asynchronous assets. Introduce checklists for code reviews that flag usage of legacy APIs (ReactDOM.render, componentWillMount) and encourage migration to hooks-based patterns.

Quality engineering must expand coverage for concurrency. Enhance unit tests with React Testing Library’s waitFor utilities and incorporate Jest’s fake timers to simulate asynchronous updates. Integration tests should verify that form submissions, optimistic updates, and routing transitions behave correctly when concurrent rendering defers updates. Establish performance budgets tracked in CI/CD pipelines, using Lighthouse CI or WebPageTest to catch regressions.

Operations teams should monitor error budgets and stability during rollout. Instrument applications with telemetry (New Relic, Datadog, Sentry) that captures render durations, component update frequencies, Suspense fallback usage, and hydration errors. Define automated rollback criteria for production deployments and rehearse canary release processes. Document incident response runbooks specific to front-end regressions triggered by the upgrade.

Sourcing, training, and ecosystem readiness

Evaluate third-party dependencies for React 18 compatibility. Maintain a vendor matrix that tracks library versions, migration guides, and active maintenance status. Prioritize upgrades or replacements for packages that rely on legacy lifecycles or patch DOM APIs directly. Engage with vendors whose SDKs integrate deeply with React (analytics, experimentation, design systems) to confirm their testing coverage under concurrent rendering. For internal component libraries, allocate capacity to update patterns, add Suspense-aware data hooks, and publish migration notes to consuming teams.

Invest in training for developers, QA engineers, and designers. Host workshops covering concurrent rendering fundamentals, the startTransition API, Suspense patterns, and streaming server rendering. Provide sandbox environments where teams can experiment with deferred rendering, caching strategies (React Query, Relay), and streaming data fetchers. Encourage contributions to shared documentation, including examples of migrating class components, handling form libraries, and integrating state managers (Redux Toolkit, Recoil, Zustand) with concurrent features.

Legal and procurement teams should review license compliance for upgraded dependencies and ensure support contracts with key vendors cover React 18-related issues. Evaluate whether to engage consulting partners or React core contributors for complex migrations, especially in regulated industries where accessibility, localization, and audit trails are critical.

Forward-looking roadmap

React 18 sets the stage for future innovations such as server components and improved data-fetching frameworks. Architecture teams should monitor the React Working Group discussions, RFCs, and roadmap updates to anticipate breaking changes or new primitives. Align with product management on how concurrency enables features like offline-first experiences, collaborative editing, or personalized content streams. Maintain alignment with accessibility standards (WCAG 2.2) by testing Suspense fallbacks with assistive technologies and ensuring transitions communicate state changes effectively.

By approaching the React 18 upgrade as a structured program—covering dependency hygiene, testing, governance, sourcing, and performance monitoring—organizations can unlock responsiveness improvements while safeguarding stability. Treat the migration as an opportunity to pay down technical debt, modernize patterns, and build confidence in the front-end platform that underpins customer experiences.

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