What Is HTTP Status Codes? SEO Glossary

HTTP status codes are three-digit numbers that a web server returns in response to every request from a browser or search engine crawler. They communicate whether a request was successful, redirected, encountered an error, or failed for a specific reason. Every time Googlebot visits one of your pages, the HTTP status code it receives determines how Google handles that URL in its index.

These codes are the language of communication between servers and clients. Understanding them is essential for SEO because the wrong status code can cause pages to be deindexed, link equity to be lost, or crawl budget to be wasted.

Why HTTP Status Codes Matter for SEO

Search engines rely on HTTP status codes to understand the state of your website. A 200 status tells Google the page is healthy and should be indexed. A 301 tells Google the page has permanently moved and its ranking signals should transfer. A 500 tells Google your server is broken and the page should not be trusted right now.

Serving the wrong status code has real consequences. If a working page accidentally returns a 404, Google will deindex it. If a permanently moved page returns a 302 instead of a 301, Google may not transfer link equity properly. If your server intermittently returns 503 errors, Google will reduce its crawl rate, slowing down how quickly your new content gets discovered.

On large sites, status code issues multiply fast. A misconfigured server rule can send wrong status codes to thousands of URLs simultaneously. Monitoring and correctly implementing status codes is one of the foundations of technical SEO.

How HTTP Status Codes Work

Status codes are grouped into five classes based on the first digit:

1xx (Informational): The request has been received and processing continues. These are rarely relevant to SEO. The most notable is 103 Early Hints, which can preload resources before the full response, improving page speed.

2xx (Success): The request was successful. The most important is 200 OK, meaning the page exists and content was delivered successfully. This is what you want Google to receive for every page you want indexed.

3xx (Redirection): The requested URL has been moved. The SEO-critical codes here are:

• 301 Moved Permanently: Transfers 95-99% of link equity to the new URL. Use for permanent URL changes.
• 302 Found: Temporary redirect. Google keeps the original URL in the index. Use when the move is genuinely temporary.
• 307 Temporary Redirect: The HTTP/1.1 equivalent of 302. Same SEO treatment.
• 308 Permanent Redirect: The HTTP/1.1 equivalent of 301. Same SEO treatment.

4xx (Client Error): The request was invalid or the resource cannot be found.

• 404 Not Found: The page does not exist. Google will eventually deindex it after repeated encounters.
• 410 Gone: The page has been permanently removed. Google deindexes faster than with 404.
• 403 Forbidden: Access is denied. Google will not index the page.
• 429 Too Many Requests: Rate limiting. Google will slow its crawl rate.

5xx (Server Error): The server failed to fulfill the request.

• 500 Internal Server Error: Generic server failure. Repeated 500s cause Google to reduce crawl frequency and may lead to deindexation.
• 502 Bad Gateway: The server acting as a gateway received an invalid response from the upstream server.
• 503 Service Unavailable: The server is temporarily down. Google will retry later without penalizing your rankings if it resolves quickly.

Best Practices for HTTP Status Codes

Ensure all live pages return 200. This sounds obvious, but misconfigurations, broken deployments, and edge cases can cause working pages to return wrong status codes. Regularly crawl your site to verify.

Use 301 for all permanent URL changes. Whenever you change a URL structure, migrate domains, or consolidate pages, 301 redirects preserve your SEO investment. Never use 302 for permanent moves.

Return 404 or 410 for genuinely removed content. Do not soft-404 pages by returning a 200 status code with "page not found" content. Google penalizes soft 404s because they waste crawl budget and confuse the index.

Handle 503 correctly during maintenance. When your site is temporarily down for maintenance, return 503 with a Retry-After header. This tells Google the downtime is temporary and to come back later. Never return 200 with a maintenance page, as Google may index that page as your actual content.

Monitor 5xx errors aggressively. Server errors are the most damaging status codes for SEO because they indicate your site is unreliable. Set up real-time alerting for spikes in 500-level errors.

Implement proper redirect chains. Avoid chains where URL A redirects to B, which redirects to C. Each hop loses a small amount of link equity and slows down both users and crawlers. Redirect directly from A to C.

Common Mistakes

Returning 200 for error pages is the most widespread mistake. Your custom 404 page should actually return a 404 HTTP status code, not a 200. Many CMS platforms and web frameworks serve a pretty "not found" page but with a 200 status, which Google calls a "soft 404." This is a significant crawl waste issue on large sites.

Using 302 redirects for permanent moves happens constantly because many developers and CMS tools default to 302. Google has gotten better at interpreting intent, but explicitly using 301 removes ambiguity.

Not handling server errors during deployments causes temporary ranking drops. If your deployment process has a window where the site returns 500 errors, Google may crawl during that window and record errors for your key pages.

Creating redirect loops where page A redirects to B and B redirects back to A makes both pages uncrawlable. Test your redirects after implementation to catch circular references.

Ignoring status codes in JavaScript-rendered sites is another gap. If your initial server response returns 200 but the client-side JavaScript renders a "not found" experience, Google may still index the empty shell page.

Conclusion

HTTP status codes are the foundation of how search engines understand your website's structure, health, and intent. Every page must return the correct status code, whether that is 200 for live content, 301 for permanently moved URLs, 404 for missing pages, or 503 for temporary downtime. Incorrect status codes waste crawl budget, lose link equity, confuse indexing, and ultimately cost you rankings. Audit your status codes regularly, monitor server errors in real time, and treat proper status code implementation as a non-negotiable part of your technical SEO foundation.