In computer networking, "HTTP 451 Unavailable For Legal Reasons" is a proposed and not yet universally adopted error status code of the HTTP protocol to be displayed when the user requests an illegal resource, such as a web page censored by a government, with the number 451 being a reference to the 1953 dystopian novel Fahrenheit 451, where books are outlawed. 451 could be described as a more descriptive variant of 403 forbidden.
Examples of situations where an HTTP 451 error code could be displayed include web pages deemed a danger to national security, or web pages deemed to violate copyright, privacy, blasphemy laws, or any other law or court order.
However, some sites may be forced to produce HTTP 404 (File Not Found) or similar, if they are not legally permitted to disclose that the resource has been removed.
- Flood, Alison (June 22, 2012). "Call for Ray Bradbury to be honoured with internet error message". The Guardian. Retrieved June 22, 2012.
- Ducklin, Paul (August 19, 2013). "HTTP error code 451: "Unavailable For Legal Reasons"". Naked Security. Sophos.
- The Guardian: Call for Ray Bradbury to be honoured with internet error message
- BoingBoing: Error Code 451: an HTTP error for censorship
- Forbes: Yes, We Should Have the 451 HTTP Status Code
- Naked Security: HTTP error code 451: "Unavailable for legal reasons"
- IETF Draft: An HTTP Status Code to Report Legal Obstacles
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