Single on HTTP 301 vs 308

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Answer

HTTP status codes 301 and 308 are both permanent redirect codes, but they differ significantly in how they handle request methods and request bodies.

What Each Code Means

HTTP 301 (Moved Permanently) indicates that the target resource has been permanently moved to a new URI. It suggests that future references to the resource should use one of the new URIs provided in the Location header. Search engines and other crawlers will update their records accordingly.

HTTP 308 (Permanent Redirect) also indicates that the target resource has been permanently moved to a new URI and that future references should use the enclosed URIs. The key difference lies in how clients handle the redirect.

Request Method and Body Handling

The fundamental difference between 301 and 308 lies in how clients treat the request method and body:

301 Moved Permanently: For historical reasons, clients (particularly browsers) are permitted to change the request method from POST to GET when following a 301 redirect. This means if you POST data to a URL that returns 301, the client may convert that to a GET request to the new location, losing the request body in the process.

308 Permanent Redirect: With 308, the request method and body must not be changed by the client. If the original request was a POST with a body, the client must send a POST with the same body to the new location. This removes the ambiguity that exists with 301 and was the primary reason 308 was created—to serve as a permanent variant of 307 (which similarly does not allow method changes, but is temporary).

Cacheability

Both status codes have the same caching behavior: both 301 and 308 responses are heuristically cacheable by default. This means they can be cached without explicit cache control headers, unless otherwise indicated by the method definition or explicit cache controls.

Current Specifications

• HTTP 301 is specified in RFC 9110 (HTTP Semantics), Section 15.4.2, and was originally defined in RFC 7231.
• HTTP 308 was introduced in RFC 7538 (April 2015) and is now included in RFC 9110 (HTTP Semantics), Section 15.4.9. RFC 7538 was created specifically to define the missing permanent variant of status code 307.

The key reason 308 was created is explained in RFC 7538: while 307 (Temporary Redirect) provides a clear specification that the method must not change, HTTP lacked a corresponding permanent redirect with this same guarantee. RFC 7538 filled this gap by adding 308 as the permanent counterpart to 307, with the same strict method preservation requirements.

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