301 vs 302 Redirects for SEO: HTTP Semantics and Link Equity

HTTP redirection is governed by the Internet Engineering Task Force (IETF) under RFC 9110: HTTP Semantics, Section 15.4. When a server returns a 3xx status code, it includes a Location header directing the client to the target URL. The critical engineering distinction between redirect types lies in two dimensions: Permanence (whether the change is permanent or temporary) and Method Handling (whether the client is permitted to change the HTTP method from POST to GET).

While historical web architectures relied solely on 301 and 302, modern HTTP standards introduced 307 and 308 to eliminate ambiguity regarding request methods. The table below details how these four redirect codes behave across both network layers and search engines:

Permanent redirects signal to both search engines and browser clients that the requested resource has definitively moved to a new canonical URL and will never return to the old address. Google Search Central documentation on redirects confirms that Google treats 301 and 308 identically for index consolidation.

Temporary redirects tell search engine spiders: 'Send users to this temporary destination right now, but keep crawling the original URL because it will return soon.' Because search engines keep the original URL indexed, backlink PageRank is not transferred to the temporary destination.

In Next.js App Router, redirects can be declared in next.config.ts, inside edge middleware.ts, or dynamically within Server Components and Route Handlers:

// 1. Dynamic Server Component Redirects
import { redirect, permanentRedirect } from "next/navigation";

export default async function LegacyPostPage({ params }: { params: { slug: string } }) {
  const isMigrated = checkMigration(params.slug);

  if (isMigrated) {
    // Emits HTTP 308 (Permanent Redirect, preserves method)
    permanentRedirect(`/blog/${getNewSlug(params.slug)}`);
  }

  // Emits HTTP 307 (Temporary Redirect, preserves method)
  if (isUnderMaintenance()) {
    redirect("/maintenance");
  }

  return <PostView slug={params.slug} />;
}

For bulk URL patterns, configure redirects() inside next.config.ts. Setting permanent: true automatically outputs HTTP 308, while permanent: false outputs HTTP 307:

// 2. Declarative Redirects in next.config.ts
import type { NextConfig } from "next";

const nextConfig: NextConfig = {
  async redirects() {
    return [
      {
        source: "/old-blog/:slug",
        destination: "/blog/:slug",
        permanent: true, // Outputs HTTP 308
      },
    ];
  },
};

export default nextConfig;

Redirect errors cause severe SEO ranking losses during site rebuilds. Review the table below to protect your organic traffic:

Execute this verification sequence whenever deploying redirect mappings or URL structure changes: