HTTP Status Codes Explained for Website Owners and SEOs

Every time a browser, crawler, app, or monitoring tool requests a URL, the server responds with an HTTP status code. That three digit number is one of the quickest ways to understand what happened to the request. It can tell you that the page loaded successfully, moved elsewhere, was not found, was blocked, or failed because of a server problem.

For technical SEO, status codes matter because search engines use them when deciding whether a URL can be crawled, whether content should be processed for indexing, whether signals should move to another URL, and whether a page appears to have disappeared. For developers and site owners, they are also a first line diagnostic tool.

How HTTP status codes are organized

Standard HTTP response codes are grouped into five classes according to their first digit:

• 1xx informational responses
• 2xx successful responses
• 3xx redirection responses
• 4xx client error responses
• 5xx server error responses

Most routine website analysis focuses on the last four groups, especially 200, 301, 302, 404, 410, 429, 500, 502, and 503.

A status code describes a specific response, not whether the page content is actually correct. A broken page can still return 200 OK, so status checks should be combined with content and indexing checks.

2xx: successful responses

200 OK

200 OK is the normal response for a page that was successfully retrieved. For a typical GET request, it means the server returned the requested representation.

For Google Search, a 200 response allows the received content to enter further processing, but it does not guarantee indexing. The page can still be excluded for other reasons such as noindex, duplication, insufficient value, canonicalization, or access problems discovered later.

A common technical mistake is returning 200 for a page that visually says "Page not found." Search engines may classify this as a soft 404 because the HTTP response says success while the content behaves like an error page.

3xx: redirects

A 3xx status tells the client that another step is needed, usually because the resource is available at another URL.

301 Moved Permanently

A 301 means the resource has permanently moved. The new destination is normally supplied through the Location response header. Permanent redirects are commonly used for URL changes, HTTPS migrations, hostname changes, and site migrations.

302 Found

A 302 represents a temporary move. The original URL is expected to remain meaningful because the destination may change later.

307 and 308

307 Temporary Redirect and 308 Permanent Redirect make method preservation explicit. If the original request uses POST, these redirect types keep the same request method at the destination. 307 is temporary and 308 is permanent.

The semantic differences matter to clients even though search engines may group permanent redirects and temporary redirects similarly for some crawling decisions.

4xx: client error responses

A 4xx response means the server considers the request unsuccessful because of something associated with the requested resource or request itself.

404 Not Found

404 means the server cannot find the requested resource. It is correct for URLs that do not exist and have no appropriate replacement.

A 404 is not automatically an SEO emergency. Problems arise when important pages return it accidentally, internal links point to missing URLs, or a moved page has a relevant replacement that should receive a redirect.

410 Gone

410 Gone explicitly indicates that a resource is no longer available and that the condition is intended to be permanent. It can be appropriate for intentionally removed content with no replacement.

401 and 403

401 Unauthorized generally indicates that authentication is required. 403 Forbidden indicates that the server refuses access to the resource. If a public page that should be crawlable unexpectedly returns 403 to search engine crawlers, a firewall, CDN rule, security plugin, or bot protection configuration may be involved.

429 Too Many Requests

429 tells a client that too many requests have been sent in a given period. Google documents that its crawlers treat 429 as a signal that the server is overloaded, similar to server error behavior. Persistent rate limiting can therefore interfere with crawling.

5xx: server errors

A 5xx status indicates that the server failed while trying to handle a request that may otherwise be valid.

500 Internal Server Error

500 is a general server failure. It can result from application exceptions, configuration problems, dependency failures, or other server side issues.

502 Bad Gateway

502 usually appears when a gateway or proxy receives an invalid response from an upstream server. In modern stacks, the public server, reverse proxy, edge platform, and application server may all be separate layers, so the failure may not originate where the browser connects.

503 Service Unavailable

503 indicates temporary unavailability, often during maintenance or overload. It is more appropriate than pretending a temporarily unavailable service is a permanent 404.

Search crawlers respond cautiously to repeated server errors. Google states that 5xx responses and 429 can cause crawling to slow temporarily. Persistent server errors can eventually affect indexed URLs as well.

Why one URL can show different status codes

A result can vary by request conditions. HTTP versus HTTPS, www versus non www, trailing slash rules, authentication, CDN routing, and bot protection can all change the response.

For example:

http://example.com/page → 301

https://example.com/page → 200

That is normal. A more complicated sequence can create unnecessary hops:

http://example.com/page → 301 → https://www.example.com/page → 301 → https://example.com/page → 200

The final page works, but the redirect path is longer than necessary.

Status codes and search engine indexing

A status code is only one part of indexability, but it is a fundamental part.

A normal indexable HTML page should generally return a successful response. Google states that a page needs to work, meaning Google receives a 200 status, as one of its minimum technical requirements for eligibility. That still does not guarantee indexing.

Permanent redirects act as strong signals that the target should be processed in place of the source. Temporary redirects are weaker signals. URLs returning standard 4xx errors are not used as indexable content, and persistent 5xx problems can reduce crawling and eventually cause URLs to disappear.

Robots rules add another layer. A page can return 200 but be blocked from crawling. It can also be crawlable while carrying a noindex directive.

How to diagnose a suspicious status code

Check the exact URL, including protocol, hostname, path, and trailing slash, then record both the first response and final destination. Inspect headers next. Redirects should include a Location target, while a 403 or 502 may reveal a CDN, firewall, or proxy layer.

Compare the result in a normal browser and an external checker. If only automated requests fail, bot protection may be involved. If every request fails, investigate hosting, DNS, proxy configuration, application logs, and recent deployments. Finally, decide whether the status is intentional or an error.

Common HTTP status mistakes

Common problems include redirecting every missing URL to the homepage, returning 200 for error templates, blocking legitimate crawlers with 403, and creating unnecessary redirect chains. A checker exposes the response, but the status only becomes useful when interpreted in context.