Common HTTP Status Codes Explained
When a browser or search engine requests a web page, the server responds with an HTTP status code - a three-digit number that signals whether the request was successful, redirected, failed, or blocked. These codes are not always visible to users, but they are crucial for search engines and SEO.
Understanding what these status codes mean helps you manage crawling, indexing, and user experience more effectively. Errors, misconfigured redirects, or inconsistent server responses can all impact SEO performance and visibility.
Why HTTP Status Codes Matter for SEO
Search engines rely on status codes to understand the condition of your pages. Some codes, like 200, indicate everything is fine. Others, like 404 or 500, suggest a problem that may prevent indexing. Redirect codes like 301 and 302 help search engines follow and interpret URL changes—but only if they’re used correctly.
Misuse or misunderstanding of these codes can lead to:
- Pages being dropped from the index
- Loss of link equity during migrations
- Poor crawl efficiency
- Broken user experiences
Monitoring status codes is an essential part of technical SEO and should be part of every audit and site health check.
2xx: Success Codes
200 OK
The most common and ideal response. It means the request was successful, the page loaded properly, and the content is accessible.
For SEO, this is what you want for all indexable and canonical URLs. Any page returning a 200 status is eligible to be crawled and indexed.
3xx: Redirection Codes
301 Moved Permanently
This is the correct response when a page has been permanently moved to a new URL. Search engines pass most (if not all) link equity through 301 redirects, and update the index to reflect the new destination.
Use 301s when:
- Redirecting deleted or outdated pages
- Consolidating URLs (e.g., non-www to www, HTTP to HTTPS)
- Changing site structure or domain
Avoid chaining multiple 301s - each step can dilute crawl efficiency.
302 Found / 307 Temporary Redirect
Both indicate a temporary redirect. Google may not transfer full link equity, and it might continue to index the original URL instead of the new one.
Use temporary redirects only if you plan to restore the original page soon. For long-term changes, always use 301 instead.
304 Not Modified
This tells the browser or crawler that the page hasn’t changed since the last request. It reduces bandwidth and crawl load, and is a healthy part of efficient crawling.
Googlebot uses 304s to avoid re-downloading unchanged resources. No SEO risk unless misconfigured.
4xx: Client Errors
404 Not Found
A standard “Page not found” error. The URL doesn’t exist and the server can’t return any content.
Google may drop 404 pages from its index over time. If a page is intentionally removed and has no suitable replacement, 404 is appropriate. However, for deleted content that has an equivalent or updated version, use a 301 redirect instead.
Too many 404s, especially linked from internal pages or external backlinks, create crawl inefficiencies and harm user experience.
410 Gone
Similar to 404, but more definitive. A 410 tells crawlers the page is intentionally removed and won’t return.
Useful when you want to de-index a page quickly, especially during content cleanups or site pruning. Google treats 410s slightly more aggressively than 404s.
403 Forbidden
The server understands the request, but refuses to authorize it. This often indicates permission issues or IP-based access restrictions.
For SEO, this can block crawlers from accessing content (even if the page exists) resulting in indexability problems.
401 Unauthorized
Requires authentication. Typically used for login-protected areas. These pages should not be accessible or indexable by search engines unless intentional.
5xx: Server Errors
500 Internal Server Error
A general error that signals something is wrong on the server side. Google may retry crawling, but repeated 500 errors can lead to deindexing of affected URLs.
Frequent or prolonged 500 errors are a high-priority technical issue.
502 Bad Gateway / 503 Service Unavailable
These indicate temporary server issues or overloads. A 503 can also be used during maintenance, and if configured properly with a Retry-After header, Google understands to try again later.
Avoid letting these errors persist—if Googlebot sees repeated server errors, it may reduce crawl frequency or drop content from the index.
504 Gateway Timeout
The server did not respond in time. Similar SEO implications as 502 and 503. Indicates reliability or hosting issues that should be resolved quickly.
How to Monitor and Manage Status Codes
- Use Google Search Console to view crawl errors, excluded pages, and coverage status.
- Crawl your site regularly with tools like Screaming Frog, Sitebulb, or Ahrefs Site Audit.
- Monitor server logs to identify unexpected response patterns or crawl issues.
- Set up alerts for spikes in 4xx or 5xx errors using uptime monitoring tools.
Redirect chains, broken links, orphaned 404s, and server reliability all tie directly into crawl health, and can be diagnosed through consistent monitoring of HTTP status codes.