301 Redirect

A 301 redirect is an HTTP response that tells the client the resource it asked for now lives permanently at the URL given in the Location header. The client fetches that URL instead, and anything that remembers addresses is expected to update its record.

What the server sends and what the client does

The status code is defined in RFC 9110, the current HTTP semantics specification. The server answers 301 and puts the new address in a Location header. A client that receives it is allowed to change a POST into a GET when it follows the redirect, which is the one behavior that separates 301 from 308, where the method has to be preserved. A 301 is also cacheable by default, so a browser or a crawler that has seen it once may go straight to the new address next time without asking again.

Three things follow for whoever runs the site. The old URL keeps answering, but only with a pointer. The new URL has to answer 200 with the content, or the redirect points at nothing. And the chain should be one hop: every extra redirect is another request a crawler may decline to make.

Permanent and temporary redirects in an index

Google’s redirect documentation treats 301 and 308 as permanent and 302, 303 and 307 as temporary. The difference is what the indexer concludes. A permanent redirect is read as a signal that the target should be the canonical URL, so the new address is what appears in results. A temporary one is followed but not read that way, and the old address can stay indexed. Google also says a meta refresh with a zero-second delay is treated as permanent, and that a JavaScript redirect is a last resort because rendering may never run.

The audit behind what 9,483 small business websites serve to an AI crawler followed redirects on every fetch, the way an assistant’s retrieval does. A site that has moved to HTTPS or dropped its www prefix without a 301 in place presents two addresses for one business, and identity is already the weak point: 43.1% of the 9,483 sites were inconsistent about name, address or phone across their own pages. This site’s own audit; the sample was drawn per metro and trade.

A common question

What happens if a site moves to HTTPS without putting a 301 in place?

The old address keeps answering on its own, so one business is presented at two addresses and an indexer has nothing telling it which one should be canonical. A permanent redirect is read as that signal, and without it the old address can stay in the index while the two records drift apart. Identity is already the weak point across small-business sites: 43.1% of the 9,483 audited were inconsistent about name, address or phone across their own pages. Retrieval follows redirects on every fetch, so the pointer has to be there.

Sources

Status code semantics: RFC 9110, section 15.4.2. Indexing behavior: Google’s redirect documentation. The identity figure is this site’s own, from its audit records; percentages describe the sample.