Lab — Developer tools
HTTP Status Guide is a free online tool that explains every common HTTP status code in plain English — what it means, when you will see it, and what to do about it — so a bare number like 403 stops being a mystery.
The five classes
1xx — Hold on, still working. 2xx — Success. 3xx — Go somewhere else. 4xx — Your request is the problem. 5xx — The server is the problem.
Find a code
Quiz — guess the code
Press “Quiz me” to start.
The first digit is the class: 1xx means "working on it", 2xx means "done", 3xx means "look over there", 4xx means "you sent something wrong", 5xx means "something broke on our side". The other two digits are the specific case. When debugging, that first digit alone usually tells you whose desk the problem belongs on.