501 may refer to any of the following:

  1. 501 is an HTTP status code for not implemented; generated because a server cannot fulfill a request or lacks the capability to recognize the request method.

  2. 501 is an area code, see our 501 area code listing for further information.

See our HTTP definition for a listing of other HTTP error codes.

  • What do I do if I get a 501 error on the Internet?

Error, HTTP, Web design terms