What's the difference between HTTP 301
and 308
status codes?
301
(Moved Permanently): This and all future requests should be directed to the given URI.
308
(Permanent Redirect): The request and all future requests should be repeated using another URI.
They seem to be similar.
301
, 302
and 307
The RFC 7231, the current reference for semantics and content of the HTTP/1.1 protocol, defines the 301
(Moved Permanently) and 302
(Found) status code, that allows the request method to be changed from POST
to GET
. This specification also defines the 307
(Temporary Redirect) status code that doesn't allow the request method to be changed from POST
to GET
.
See more details below:
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. [...]Note: For historical reasons, a user agent MAY change the request method from
POST
toGET
for the subsequent request. If this behavior is undesired, the307
(Temporary Redirect) status code can be used instead.
The
302
(Found) status code indicates that the target resource resides temporarily under a different URI. Since the redirection might be altered on occasion, the client ought to continue to use the effective request URI for future requests. [...]Note: For historical reasons, a user agent MAY change the request method from
POST
toGET
for the subsequent request. If this behavior is undesired, the307
(Temporary Redirect) status code can be used instead.
The
307
(Temporary Redirect) status code indicates that the target resource resides temporarily under a different URI and the user agent MUST NOT change the request method if it performs an automatic redirection to that URI. Since the redirection can change over time, the client ought to continue using the original effective request URI for future requests. [...]Note: This status code is similar to
302
(Found), except that it does not allow changing the request method fromPOST
toGET
. This specification defines no equivalent counterpart for301
(Moved Permanently) (RFC 7238, however, defines the status code308
(Permanent Redirect) for this purpose).
POST
to GET
The "historical reasons" in which a user agent may change a request from POST
to GET
is explained in an Eric Lawrence's post from the IEInternals blog, dated from 19 August 2011.
The post quotes the definition of the status code 301
from the obsolete RFC 1945, published in May 1996, which defined the HTTP/1.0. The key part from that quote is:
Note: When automatically redirecting a
POST
request after receiving a301
status code, some existing user agents will erroneously change it into aGET
request.
Then the author continues:
[...] those “user agents” referred to in this remark included the popular browsers of the day, including Netscape Navigator and Internet Explorer. Arguably, this behavior is exactly what most websites wanted — after a successful
POST
, send the user to a different URL to show them something else. However, thePOST
-converted-to-GET
behavior isn’t what the authors of HTTP had intended.
308
The RFC 7238 has been created to define the 308
(Permanent Redirect) status code, that is similar to 301
(Moved Permanently) but does not allows the request method to be changed from POST
to GET
.
The 308
status code is now defined by the RFC 7538 (that obsoleted the RFC 7238).
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. Clients with link editing capabilities ought to automatically re-link references to the effective request URI to one or more of the new references sent by the server, where possible. [...]Note: This status code is similar to
301
(Moved Permanently), except that it does not allow changing the request method fromPOST
toGET
.
So we have the following:
+-----------+-----------+
| Permanent | Temporary |
+------------------------------------------------------------+-----------+-----------+
| Allows changing the request method from POST to GET | 301 | 302 |
+------------------------------------------------------------+-----------+-----------+
| Doesn't allow changing the request method from POST to GET | 308 | 307 |
+------------------------------------------------------------+-----------+-----------+
Michael Kropat put together a set of decision charts that helps to determine the best status code for each situation. See the following for 2xx
and 3xx
status codes: