Redirect & 404 Handling SEO Guidelines

Follow these rules when implementing redirects or handling missing pages.

Redirect Types

Code	Name	When to use
301	Permanent	URL has permanently changed — product renamed, section restructured
308	Permanent (preserves method)	Same as 301 but preserves POST/PUT — use for API redirects
302	Temporary (default in Next.js)	Temporary redirect — locale detection, A/B tests, maintenance
307	Temporary (preserves method)	Same as 302 but preserves POST/PUT

Default rule: Use 301 for permanent URL changes (most common SEO case). Use 302 for locale detection redirects. Never use 302 when you mean 301 — it delays canonicalization and signals the wrong intent to search engines.

Next.js Redirects in next.config.js

For simple, static redirect patterns:

// next.config.js
module.exports = {
  async redirects() {
    return [
      // Old product URL pattern to new
      {
        source: '/:locale/old-products/:id',
        destination: '/:locale/products/:id',
        permanent: true, // 301
      },
      // Removed page to replacement
      {
        source: '/:locale/about-us',
        destination: '/:locale/contact-us',
        permanent: true,
      },
      // Regex pattern for old category structure
      {
        source: '/:locale/shop/:category',
        destination: '/:locale/categories/:category',
        permanent: true,
      },
    ];
  },
};

Use next.config.js redirects when: The pattern is simple, applies to all requests, and doesn't need request-time logic.

Middleware Redirects

For complex, dynamic redirect logic:

// middleware.ts
import { NextRequest, NextResponse } from 'next/server';

export function middleware(request: NextRequest) {
  const { pathname } = request.nextUrl;

  // Locale detection — TEMPORARY redirect (302)
  if (pathname === '/') {
    const locale = detectLocale(request) || DEFAULT_LOCALE;
    return NextResponse.redirect(new URL(`/${locale}/`, request.url), 302);
  }

  // Old product URL migration — PERMANENT redirect (301)
  const oldProductMatch = pathname.match(/^\/(\w{2}-\w{2})\/old-products\/(\d+)/);
  if (oldProductMatch) {
    const [, locale, id] = oldProductMatch;
    return NextResponse.redirect(
      new URL(`/${locale}/products/${id}`, request.url),
      301
    );
  }
}

Use middleware redirects when: You need request-time logic (headers, cookies, geo-detection) or complex matching.

Redirect Chains

Never create redirect chains — where URL A redirects to B, which redirects to C.

BAD:  /old-page → /moved-page → /final-page  (chain)
GOOD: /old-page → /final-page  (direct)
      /moved-page → /final-page  (direct)

Redirect chains:

• Slow down page load (each redirect adds a network round trip)
• Waste crawl budget — Googlebot may stop following after several hops
• Confuse search engine crawlers and delay canonicalization

When migrating URLs, always redirect to the final destination, even if there were intermediate moves.

Canonical vs Redirect

Scenario	Solution
Two URLs serve the same content, both should remain accessible	Use canonical on both pointing to the preferred URL
An old URL should no longer be used	301 redirect to the new URL
Trailing slash vs non-trailing slash	Pick one, redirect the other
HTTP to HTTPS	301 redirect HTTP to HTTPS
www to non-www (or vice versa)	301 redirect to the canonical domain
Filter params creating duplicate content	Set canonical to the base category URL

404 Handling

• Custom 404 page with useful navigation — help users find what they were looking for
• Never redirect 404s to the homepage — it sends a false "200 OK" signal and confuses search engines
• Return actual 404 status code — Google needs to see 404 to remove old URLs from the index
• Include in the 404 page: search box, top categories, popular products, contact link

// Not found page (app/[locale]/not-found.tsx or pages/404.tsx)
export default function NotFound() {
  return (
    <div>
      <h1>Page Not Found</h1>
      <p>The page you're looking for doesn't exist or has been moved.</p>
      <nav>
        <h2>Popular Categories</h2>
        <ul>
          <li><Link href="./categories/electronics">Electronics</Link></li>
          <li><Link href="./categories/accessories">Accessories</Link></li>
          <li><Link href="./contact-us">Contact Us</Link></li>
        </ul>
      </nav>
    </div>
  );
}

Locale Redirects

• Root / → detected locale — use 302 (temporary), not 301
• Locale mismatch — if a user manually navigates to a wrong locale, do NOT auto-redirect; let them stay (they may be comparing prices or using a different language on purpose)
• Non-existent locale — /xx-YY/products/123 should 404, not redirect to a default locale

// middleware.ts — locale redirect rules
export function middleware(request: NextRequest) {
  const pathname = request.nextUrl.pathname;

  // Only redirect the bare root
  if (pathname === '/') {
    const locale = detectLocaleFromHeaders(request) || DEFAULT_LOCALE;
    return NextResponse.redirect(new URL(`/${locale}/`, request.url), 302);
  }

  // Validate locale prefix
  const localeMatch = pathname.match(/^\/([a-z]{2}-[A-Z]{2})\//);
  if (localeMatch && !ALL_LOCALES.includes(localeMatch[1])) {
    // Invalid locale — return 404, don't redirect
    return NextResponse.rewrite(new URL('/not-found', request.url));
  }
}

HTTPS and Domain Redirects

• All HTTP requests must 301 redirect to HTTPS (typically handled at CDN/infrastructure level)
• Ensure consistent domain — no duplicate content between www and non-www variants

Common Mistakes to Avoid

1. 302 for permanent moves — always use 301 for permanent URL changes
2. Redirect chains — always redirect directly to the final URL
3. Redirecting 404s to homepage — return proper 404 status with helpful content
4. 301 for locale detection — use 302 (user preference may change)
5. Missing redirects after URL change — if you rename a slug or move a section, add redirects for old URLs
6. Redirect loops — page A redirects to B, B redirects to A (crashes the browser)
7. Redirecting with query params — don't strip important query params during redirects without intent