Nice intro. This was my favorite for a while: https://www.jmarshall.com/easy/http/

Does anyone know of a similar tutorial covering HTTP/2 and HTTP/3 as well but in a easy-to-process language?

That's a nice piece, I got an idea to base one our tech interview question on it.

Nit: the quote by Joel Spolsky is not about leaking some sensitive data to third party, but about completely unrelated subject: leaking of underlying complexity through programming abstraction designed to hide it.

Author here: thanks!

I was hoping to get across exactly that meaning of leaky: that HTTP shows information from, and allows control of, parts of the otherwise-abstracted-away lower-levels, e.g. TCP/IP. Will see if I can make that clearer.