Look up a status, pick the right one for an API, or hit a live endpoint that actually returns it. Add ?code=418 to this URL and the response is that status — useful for curl, interceptors, and “what does my client do on 503?” Nothing here phones home except the Try it fetch to this same page.
Which class?
The request was sent to a server that cannot produce a response — typically the wrong HTTP/2 connection or SNI host.
When to use
Connection coalescing / wrong certificate host. Infrastructure, not business logic.
Don’t
Wrong URL on the right host is 404.
Live URL
curl -i https://corecoding.com/utilities/http-status.php?code=421
No codes match.
Code use cases