# Vercel React Best Practices

React and Next.js performance optimization guidelines maintained by Vercel Engineering, covering 70 rules organized into 8 priority-based categories.

## When to Reference

Apply these guidelines when writing new components, implementing data fetching, reviewing performance, refactoring code, or optimizing bundle size and load times.

## Key Categories

### Critical Priority

**Eliminating Waterfalls**
Address async bottlenecks like sequential awaits. Use Suspense for streaming. Parallelize data fetches where possible.

**Bundle Size Optimization**
Use direct named imports, dynamic loading (`next/dynamic`), and conditional module loading to keep bundles lean.

### High Priority

**Server-Side Performance**
Leverage `React.cache()`, LRU caching, and parallel data fetching in server components. Avoid redundant DB calls by colocating queries.

### Medium-High Priority

**Client-Side Data Fetching**
Request deduplication via SWR or TanStack Query. Optimize event listener management. Avoid useEffect for data that can be fetched server-side.

### Medium Priority

**Re-render Optimization**
Apply `useMemo`, `useCallback`, and `memo` judiciously. Manage dependency arrays carefully. Use `useTransition` to defer expensive state updates.

**Rendering Performance**
Optimize CSS for paint performance. Use `content-visibility` for off-screen content. Apply selective hydration strategies.

### Lower Priority

**JavaScript Performance**
Batch DOM updates. Cache repeated computations. Use efficient data structures for lookups.

**Advanced Patterns**
Use event handler refs for stable callbacks. Apply initialization patterns that avoid unnecessary re-renders on mount.

## Rule Format

Each rule includes:
- A description of the problem
- Incorrect code example
- Correct code example
- Additional context and links to deeper documentation

## Installation

```bash
npx skills add https://github.com/vercel-labs/agent-skills --skill vercel-react-best-practices
```

---

*Mirrored from [https://github.com/vercel-labs/agent-skills](https://github.com/vercel-labs/agent-skills) — original author: **vercel-labs**, license: **MIT**.*
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