Fix 404 errors and missing routes in Next.js
Routes returning 404 in Next.js usually stem from incorrect file naming, misconfigured route groups, or middleware redirects. The App Router's file-based routing has strict conventions that must be followed exactly.
Error messages you might see
404 This page could not be found.Error: No route matches URL "/path"Why this happens in AI-generated code
Incorrect file naming convention
AI-generated route files often use wrong names like index.tsx instead of page.tsx in the App Router, or miss the required folder structure entirely.
Route groups or parallel routes misconfigured
AI tools create route group folders with incorrect parentheses syntax or nested layouts that inadvertently shadow existing routes.
Middleware redirecting or rewriting unexpectedly
AI-generated middleware may include catch-all matchers that intercept routes before they reach your page components, returning 404s or redirects.
How to fix it
Verify file structure matches App Router conventions
Ensure each route has a page.tsx (not index.tsx) inside the correct directory. Route groups use (parentheses), dynamic segments use [brackets].
Check middleware matcher configuration
Review your middleware.ts matcher config to ensure it isn't intercepting the routes that return 404. Use console.log in middleware to trace requests.
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Frequently asked questions
Why does my route work in dev but 404 in production?
Production builds pre-render static routes at build time. If a dynamic route doesn't have generateStaticParams or isn't configured for dynamic rendering, it may not be available at runtime.
How do I create a catch-all 404 page in the App Router?
Create a not-found.tsx file in your app directory. For nested 404 handling, add not-found.tsx inside specific route segments.
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