Mã trạng thái HTTP

A searchable reference of HTTP status codes, the three-digit numbers a server returns with every response to say what happened, from 1xx through 5xx, with their standard messages and grouped by category.

It is a fast lookup while you build or debug an API or website: type a code or part of its name and the matching entries appear, so you do not have to remember every number.

The categories tell you most of the story at a glance: 1xx informational, 2xx success, 3xx redirection, 4xx client errors (the request was wrong) and 5xx server errors (the server failed). Each group is shown in its own color so you can scan quickly.

Some codes come up constantly: 200 OK, 201 Created, 301 and 302 redirects, 304 Not Modified for caching, 400 Bad Request, 401 and 403 for auth, 404 Not Found, 409 Conflict, 422 for validation, 429 Too Many Requests, and 500, 502 and 503 on the server side.

A frequent source of confusion is 401 versus 403: 401 Unauthorized means you have not authenticated, while 403 Forbidden means you are authenticated but not allowed. Another is 301 versus 302: a permanent versus a temporary redirect, which search engines treat very differently.

The reference is static data shipped with the page, so searching is instant and works offline.