This is a personal bookmark. I got tired of searching for the same subnet mask, HTTP status or signal number every few weeks, so I put the tables I actually use on one page and host it myself.
Everything is hand-written HTML and one CSS file. There is no JavaScript, no cookies, no analytics, no comments and no accounts. The server only logs what nginx logs by default.
Sources are the usual RFCs and man pages: RFC 791 / 4632 for addressing, RFC 9110 for HTTP, signal(7) and chmod(1) for the Unix bits, the IANA port registry and the BIPM SI brochure. If something is wrong, it is my transcription, not theirs.
Content is free to copy. Attribution is nice but not required.