301 and 308: two types of permanent redirect

Useful to know

Changing an address on a site does not require old links to immediately become useless. The server can answer that the resource has been moved, and indicate where to be searched. The status 301 denotes permanent relocation, and the Location header contains the new address. The browser usually makes a next request to it. It's more than showing a message: there is a second network action that needs to be completed successfully in order for the visitor to see the expected page. [1]

The 308 status also means permanent redirection. Its important feature is the preservation of the method and body of the request when moving to the new address. [2] The difference becomes essential when the exchange is not just opening a document. If a client is sending data, it matters if they send the same action with the same content after the redirect. The apparent similarity between two pages is not enough to assume that the two statuses are interchangeable in each stream.

At 301, there is an established behavior in which POST is converted to GET when following the redirection. MDN recommends 308 when changing the method should be avoided. [1] This does not mean that every site should mechanically replace all of its redirects. It is necessary to first understand what queries go through the specific rule. Moving a public article and redirecting an address to send a form have different contexts, although both use a new URL.

Consider a fictional example with a changed path of catalog material. The old address returns a redirect to the new one, but the new path in turn returns another redirect. You get a chain of requests. This example shows why the verification does not end at the first status. You need to see the final address and the final answer. If two rules point to each other, the presence of correctly written codes alone will not give a complete boot.

In a technical check, it is useful to separately consider the initial response and subsequent follow-up. This shows whether Location is the expected value and whether the method is kept where it is needed. The specificity of the 308 is precisely in the client's behavior at the next request, not in the beautiful message in the body. [2] For sensitive actions, the test must use safe test data to observe the result without accidentally creating real records.

For the maintenance of the site, a good rule has a clear occasion and a clear purpose: which old address it serves, which new one it leads to and why the move is permanent. After a change, representative links and necessary methods can be checked, instead of relying only on the home page. Thus, redirection remains a predictable part of the address architecture. It helps visitors reach the content when the site is developing, without the old paths becoming a vague maze of rules.