Next.js Common Production Errors and How to Fix Them

Why Next.js production errors are unique

Next.js has different behavior in production vs development: no hot reload, optimized builds, SSR/SSG differences, edge runtime restrictions, and stricter caching. Errors that don't occur in dev hit users in prod.

Error: Cannot find module

Usually a case-sensitivity issue. Linux (production) is case-sensitive, macOS (development) is not. Your import works locally, fails on the server. Fix: consistent casing in all import paths.

ReferenceError: window is not defined

You're using browser APIs in code that runs server-side. Fix: check typeof window !== "undefined" before using browser APIs, or use next/dynamic with ssr: false.

Error: Hydration failed

Mismatch between server and client render. Common causes: browser extensions modifying DOM, conditional rendering based on client-only state, Date.now() or Math.random() in render. Fix: use useEffect for client-only content.

Build error: Type error in production types

TypeScript errors that were ignored locally fail CI/CD build. Fix: run tsc --noEmit locally before committing.

API Route 500 on first request after cold start

Database connection not established before first request. Fix: move DB client initialization outside the handler function.

Tracking Next.js errors with ProdFix

Install @prodfix/sdk in your Next.js app and add it to _app.tsx or layout.tsx. All client and server errors are captured with full context including the route and any SSR data.