301 Moved Permanently
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.
The server SHOULD generate a Location header field in the response containing a preferred URI reference for the new permanent URI. The user agent MAY use the Location field value for automatic redirection. The server's response payload usually contains a short hypertext note with a hyperlink to the new URI(s).
Note: For historical reasons, a user agent MAY change the request method from POST to GET for the subsequent request. If this behavior is undesired, the 307 Temporary Redirect status code can be used instead.
A 301 response is cacheable by default; i.e., unless otherwise indicated by the method definition or explicit cache controls1.
301 Code References
Rails HTTP Status Symbol
Go HTTP Status Constant
Symfony HTTP Status Constant