HTTP Cats

I love how there is a Catalan version too! I guess it’s probably a requirement for getting the .cat domain.

HTTP 000: HTTP not found. HTTPS CA TLS only.

That said, at least they have a broad cipher set support and their HTTPS-only implemetation does work in older browsers and systems. That's nice. But HTTP+HTTPS would be better.

There's an alternative[0] for the canine lovers.

[0]: https://httpstatusdogs.com

Not to be confused with Cat as a Service - https://cataas.com/

Your browser (if you're using one of the "usual ones") doesn't really do much with the response's status code if it doesn't match a few specific ones for redirecting/caching/protocol shenanigans.

Anything in the 4XX range is going to be treated as just a regular ol' response, just like 404. (You could serve an entire site with all responses set to status=404, and be fine... other than probably never getting any cache hits) If you don't include a body in the response, the browser might sub in it's own error page, but it will just communicate that the user agent made a bad request.