Plan-execute on HTTP 301 vs 308

Based on my research of the authoritative specifications, I can now provide you with a comprehensive explanation of the differences between HTTP status codes 301 and 308.

HTTP Status Codes 301 vs 308: A Complete Comparison

What Each Status Code Means

Both 301 (Moved Permanently) and 308 (Permanent Redirect) indicate that a resource has been permanently moved to a new URI. According to RFC 7231, "The 301 (Moved Permanently) status code indicates that the target resource has been assigned a new permanent URI and any future references to this resource ought to use one of the enclosed URIs." Similarly, RFC 7538 states that "The 308 (Permanent Redirect) status code indicates that the target resource has been assigned a new permanent URI and any future references to this resource ought to use one of the enclosed URIs."

The critical difference between these codes lies in how clients should handle the request method and body when following the redirect.

Request Method and Body Handling

301 Moved Permanently permits clients to change the request method. RFC 7231 explicitly notes: "For historical reasons, a user agent MAY change the request method from POST to GET for the subsequent request." This flexibility means that when a client receives a 301 response to a POST request, it may convert that to a GET request when following the redirect. This is a historical artifact of how HTTP was implemented in early browsers.

308 Permanent Redirect, by contrast, does not allow such changes. RFC 7538 makes this clear: "This status code is similar to 301 (Moved Permanently), except that it does not allow changing the request method from POST to GET." The 308 status code was specifically created to provide a permanent redirect that preserves the request method and body exactly as they were in the original request. As RFC 9110 explains, "307 (Temporary Redirect) and 308 (Permanent Redirect) [RFC7538] were later added to unambiguously indicate method-preserving redirects."

Cacheability

Both status codes are cacheable, though the terminology differs between specifications. RFC 7231 and RFC 7538 state that 301 and 308 responses are "cacheable by default; i.e., unless otherwise indicated by the method definition or explicit cache controls." RFC 9111 (the current caching specification) clarifies this terminology: "Note that in previous specifications, heuristically cacheable response status codes were called 'cacheable by default'." Both codes are now described as "heuristically cacheable" in RFC 9110, meaning they can be reused by a cache even without explicit freshness information, though caches must still respect explicit cache control directives.

Official Specifications

HTTP Status Code 301 is currently specified in RFC 9110 (HTTP Semantics), which supersedes the earlier RFC 7231 (Hypertext Transfer Protocol (HTTP/1.1): Semantics and Content). RFC 7231 originally defined 301.

HTTP Status Code 308 was introduced in RFC 7538 (The Hypertext Transfer Protocol Status Code 308 (Permanent Redirect)), published in April 2015. It is also now included in RFC 9110. RFC 7538 was created specifically to fill a gap: RFC 7231 noted in its discussion of 307 that "This specification defines no equivalent counterpart for 301 (Moved Permanently)," and RFC 7538 was written to provide exactly that—a permanent redirect that preserves request methods, parallel to how 307 (Temporary Redirect) preserves them.

The key reason 308 was created is illustrated in RFC 7538's classification table, which shows that 301 "allows changing the request method from POST to GET" while 307 "does not allow changing the request method from POST to GET," but there was no permanent variant of 307. The 308 status code completed this matrix.

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