status Obsoleted
Verified 2026-09-18 · registry updated 2025-09-15

HTTP 510 Not Extended (Obsoleted)

The former extension mechanism response is obsolete and should not be used for new protocols.

Do not use 510 in new applications; it is retained as an obsoleted registry entry.

httpstatus codeprotocolobsolete

Response (http)

HTTP/1.1 510 Not Extended (Obsoleted)

The current HTTP registry retains 510 Not Extended (Obsoleted) as obsolete. Do not use it in a new protocol.

Common mistakes

  • Sending 510 as a normal application response.

Registry reference: RFC 2774; status changed to Historic

Sources

Permalink: https://merginit.com/reference/http/status-510