react-best-practices

React Best Practices (Vercel)

Overview

Use this skill to apply Vercel’s React/Next.js performance rules. The goal is to eliminate waterfalls, reduce bundle size, and keep server/client work efficient.

When to Use

• Building or reviewing React components or Next.js pages
• Adding data fetching (server or client)
• Optimizing bundle size or load time
• Investigating rendering or re-render performance issues

Quick Reference (Rule Categories)

Core Checks (Most Common)

• Waterfalls: Look for sequential await where operations are independent → use Promise.all.
• Bundle size: Avoid barrel imports, dynamically import heavy components.
• Server fetches: Start promises early, await late; use React cache where applicable.
• Re-renders: Memoize expensive components and avoid derived-state subscriptions.

Rule Pointers (Most Used)

• async-parallel, async-defer-await, async-api-routes
• bundle-barrel-imports, bundle-dynamic-imports, bundle-defer-third-party
• server-cache-react, server-parallel-fetching, server-serialization
• client-swr-dedup, rerender-memo, rerender-dependencies

Full reference: https://github.com/vercel-labs/agent-skills/tree/main/skills/react-best-practices

Example Application

If a Next.js server component does:

• await getUser()
• await getNotes()

and these are independent, apply async-parallel and fetch with Promise.all.

Common Mistakes

• Treating sequential await as harmless when requests are independent.
• Importing from barrel files for convenience and shipping unused code.
• Passing large objects to client components instead of slimming data.

Red Flags (Stop and Apply This Skill)

• “This page feels slow but I can’t see why.”
• “We have multiple awaits in a row.”
• “Bundle size grew after adding a component.”
• “This component re-renders more than expected.”