Vercel React Best Practices

What This Skill Does

This skill provides a comprehensive performance optimization guide for React and Next.js applications, based on Vercel's best practices. It helps developers identify and address performance bottlenecks by providing prioritized rules across various categories, enabling automated refactoring and code generation for improved application performance.

When to Use

• Write new React components or Next.js pages.
• Implement data fetching strategies.
• Review code for performance issues.
• Refactor existing React/Next.js code.
• Optimize bundle size and load times.
• Improve server-side performance.

Key Features

• Covers 64 rules across 8 categories.
• Prioritizes rules by impact.
• Includes rules for eliminating waterfalls.
• Provides bundle size optimization techniques.
• Offers server-side performance enhancements.
• Addresses client-side data fetching optimization.

Manual Installation

Comprehensive performance optimization guide for React and Next.js applications, maintained by Vercel. Contains 64 rules across 8 categories, prioritized by impact to guide automated refactoring and code generation.

When to Apply

Reference these guidelines when: Writing new React components or Next.js pages Implementing data fetching (client or server-side) Reviewing code for performance issues Refactoring existing React/Next.js code Optimizing bundle size or load times

Rule Categories by Priority

Quick Reference

1. Eliminating Waterfalls (CRITICAL)

async-defer-await - Move await into branches where actually used async-parallel - Use Promise.all() for independent operations async-dependencies - Use better-all for partial dependencies async-api-routes - Start promises early, await late in API routes async-suspense-boundaries - Use Suspense to stream content

2. Bundle Size Optimization (CRITICAL)

bundle-barrel-imports - Import directly, avoid barrel files bundle-dynamic-imports - Use next/dynamic for heavy components bundle-defer-third-party - Load analytics/logging after hydration bundle-conditional - Load modules only when feature is activated bundle-preload - Preload on hover/focus for perceived speed

3. Server-Side Performance (HIGH)

server-auth-actions - Authenticate server actions like API routes server-cache-react - Use React.cache() for per-request deduplication server-cache-lru - Use LRU cache for cross-request caching server-dedup-props - Avoid duplicate serialization in RSC props server-hoist-static-io - Hoist static I/O (fonts, logos) to module level server-serialization - Minimize data passed to client components server-parallel-fetching - Restructure components to parallelize fetches server-after-nonblocking - Use after() for non-blocking operations

4. Client-Side Data Fetching (MEDIUM-HIGH)

client-swr-dedup - Use SWR for automatic request deduplication client-event-listeners - Deduplicate global event listeners client-passive-event-listeners - Use passive listeners for scroll client-localstorage-schema - Version and minimize localStorage data

5. Re-render Optimization (MEDIUM)

rerender-defer-reads - Don't subscribe to state only used in callbacks rerender-memo - Extract expensive work into memoized components rerender-memo-with-default-value - Hoist default non-primitive props rerender-dependencies - Use primitive dependencies in effects rerender-derived-state - Subscribe to derived booleans, not raw values rerender-derived-state-no-effect - Derive state during render, not effects rerender-functional-setstate - Use functional setState for stable callbacks rerender-lazy-state-init - Pass function to useState for expensive values rerender-simple-expression-in-memo - Avoid memo for simple primitives rerender-split-combined-hooks - Split hooks with independent dependencies rerender-move-effect-to-event - Put interaction logic in event handlers rerender-transitions - Use startTransition for non-urgent updates rerender-use-deferred-value - Defer expensive renders to keep input responsive rerender-use-ref-transient-values - Use refs for transient frequent values rerender-no-inline-components - Don't define components inside components

6. Rendering Performance (MEDIUM)

rendering-animate-svg-wrapper - Animate div wrapper, not SVG element rendering-content-visibility - Use content-visibility for long lists rendering-hoist-jsx - Extract static JSX outside components rendering-svg-precision - Reduce SVG coordinate precision rendering-hydration-no-flicker - Use inline script for client-only data rendering-hydration-suppress-warning - Suppress expected mismatches rendering-activity - Use Activity component for show/hide rendering-conditional-render - Use ternary, not && for conditionals rendering-usetransition-loading - Prefer useTransition for loading state rendering-resource-hints - Use React DOM resource hints for preloading rendering-script-defer-async - Use defer or async on script tags

7. JavaScript Performance (LOW-MEDIUM)

js-batch-dom-css - Group CSS changes via classes or cssText js-index-maps - Build Map for repeated lookups js-cache-property-access - Cache object properties in loops js-cache-function-results - Cache function results in module-level Map js-cache-storage - Cache localStorage/sessionStorage reads js-combine-iterations - Combine multiple filter/map into one loop js-length-check-first - Check array length before expensive comparison js-early-exit - Return early from functions js-hoist-regexp - Hoist RegExp creation outside loops js-min-max-loop - Use loop for min/max instead of sort js-set-map-lookups - Use Set/Map for O(1) lookups js-tosorted-immutable - Use toSorted() for immutability js-flatmap-filter - Use flatMap to map and filter in one pass

8. Advanced Patterns (LOW)

advanced-event-handler-refs - Store event handlers in refs advanced-init-once - Initialize app once per app load advanced-use-latest - useLatest for stable callback refs

How to Use

Read individual rule files for detailed explanations and code examples:

rules/async-parallel.md rules/bundle-barrel-imports.md

Each rule file contains: Brief explanation of why it matters Incorrect code example with explanation Correct code example with explanation Additional context and references

Full Compiled Document

For the complete guide with all rules expanded: AGENTS.m Vercel React Best Practices

Comprehensive performance optimization guide for React and Next.js applications, maintained by Vercel. Contains 64 rules across 8 categories, prioritized by impact to guide automated refactoring and code generation.

When to Apply

Reference these guidelines when: Writing new React components or Next.js pages Implementing data fetching (client or server-side) Reviewing code for performance issues Refactoring existing React/Next.js code Optimizing bundle size or load times

Rule Categories by Priority

Quick Reference

1. Eliminating