419 Page Expired
Meaning
A non-standard status code used by some frameworks (e.g., Laravel) to indicate that a session or token has expired.
When to Use
When a CSRF token or session has expired and the server rejects the request for security reasons, frameworks like Laravel use 419 to signify this client-side issue.
Example
In Laravel, an AJAX request with an expired CSRF token returns 419 Page Expired, prompting the client to refresh or reauthenticate.
When Not to Use
Do not use outside of specific frameworks or contexts that expect 419. For standard HTTP, there's no official 419 code; other codes like 401 or 403 might be used depending on the scenario.
Source
Unofficial (Laravel Framework)