The status code category 3xx Redirection is divided into eight HTTP status codes. The status code category 3xx informs the inquiring client that additional measures are required in order to finish the request, as the target has been moved to a different location, for example, and can now be accessed at this new source (URL).
The corresponding HTTP status code describes the state of the redirection.
|300||Multiple Choices||The webserver has multiple possible responses to an inquiry, since the requested resource is available in different types.|
|301||Moved Permanently||The requested resource can no longer be found at URL A, because it was permanently moved to URL B and can be found there from now on. The address URL A is no longer valid.|
|302||Found (Temporarily displaced)||The requested resource is available on the webserver, but is temporarily not found at URL A, but through URL B. The address of URL A remains valid.|
|303||See Other (open other storage location)||The webserver informs the inquiring client that a separate GET request to another storage location has to be send to receive the desired resource.|
|304||Not Modified||Since the last inquiry from the client to the webserver, the resource hasn't changed and will therefore not be transmitted again.|
|305||Use Proxy||The webserver informs the client, that the request resource is only accessible through a proxy.|
|306||(reserved)||Used to be the instruction to change the proxy. At the moment, the status code is not in use, but is reserved.|
|307||Temporary Redirect||(similar to 302/303) The requested resource is available on the webserver, but is temporarily not found at URL A, but at URL B. The address of URL A remains valid. However, the browser should follow with the same method as for the original request (that means a POST is followed by a POST).|
The HTTP status code 301 Moved Permanently, also called 301 Redirect, is often used as part of the OnPage Optimization of a site, in order to redirect old (no longer valid) URLs to specific (newly created) counterparts, if changes to the URL structure are introduced. This approach is also recommended by Google.