In short. HTTP status codes describe request outcomes, while Google documents how specific responses affect content processing, redirects and index removal.

Definition: An HTTP status code is a three-digit number in a Hypertext Transfer Protocol (HTTP) response that describes the result of a request. RFC 9110, HTTP Semantics defines response classes according to the code's first digit.

Key facts

Valid status codes range from 100 to 599, according to RFC 9110.
As of 17 October 2026, Google's HTTP status documentation describes 2xx responses as eligible for processing, with indexing dependent on further evaluation.
Google's redirect documentation lists 301 and 308 as permanent redirects that signal which destination should be canonical, meaning the URL selected for search results.

What do the response classes mean?

RFC 9110 defines 1xx as informational responses sent before a final response. The 2xx class means the request succeeds; 3xx requires further action to complete it. The 4xx class covers client errors, including requests that cannot be fulfilled. The 5xx class covers server failures while fulfilling an apparently valid request.

The class gives the broad outcome. Individual codes specify what happens: 200 OK reports success, while 204 No Content carries no response content.

How do success and cached responses affect indexing?

Google's HTTP status documentation says 200 sends received content to the indexing pipeline. An empty page or error message can produce a soft 404, Google's classification for apparent missing content. A 204 supplies no content for processing.

A conditional request asks the server to respond according to conditions concerning the resource. Under RFC 9110, 304 Not Modified allows reuse of a valid stored representation without transferring it again. This response contains no content.

How do redirects change the URL processed?

Google's redirect guide distinguishes permanent redirects (301, 308) from temporary redirects (302, 303, 307). Permanent redirects signal that the destination should be canonical. Temporary redirects leave the destination eligible for indexing through other canonicalization signals.

A response using the status and header values in the guide's PHP example looks like this:

HTTP/1.1 301 Moved Permanently
Location: https://www.example.com/newurl

The Location header identifies the destination. The guide recommends permanent server-side redirects when a page's URL needs to change in search results.

What happens when content is missing or unavailable?

RFC 9110 defines 404 Not Found for a missing current representation or an unwillingness to disclose one. 410 Gone indicates that access is unavailable and likely permanently so. 503 Service Unavailable covers temporary overload or scheduled maintenance; a Retry-After header can suggest when to retry.

Google's HTTP status documentation says 4xx responses, except 429, lead to removal of indexed URLs. For 5xx and 429, crawlers temporarily slow down. Persistent server errors eventually cause indexed URLs to be dropped.

FAQ

Should I use 401 or 403 to reduce Google's crawling?

Google's HTTP status documentation advises against this. It treats 429 as an overload signal; other 4xx codes have no effect on the crawl rate.

Can I use a temporary redirect while a service is unavailable?

Google's redirect guide gives an unavailable service as an example: a temporary redirect sends visitors to a page explaining the interruption. The guide lists 302, 303, and 307 as temporary server-side redirects.

Sources

Check how a page reads to answer engines. Open the GEO score analyzer