HTTP Status Code Reference
Look up a code, search by keyword, or filter by 1xx–5xx — each entry lists the Chinese and English names plus the RFC that defines it.
How to Use
- Look up a code
Type a three-digit code like 404 and the detail panel above shows the name, Chinese name, class, RFC and explanation, while the list below shows related entries.
- Search by keyword
Words like timeout, cache or redirect match across names and descriptions — useful when you know the symptom but not the code.
- Filter by class
The 1xx to 5xx buttons narrow the list to one class, which makes "is this a client or a server problem" obvious at a glance.
FAQ
401 or 403 — which one?
401 means "I do not know who you are": no credentials or invalid ones, so the client should log in again. 403 means "I know who you are but you cannot do this": insufficient permission, and logging in again will not help. In API design, return 401 on an expired token so the client refreshes, and 403 when permission is missing so it shows a denial message.
301 versus 308?
Both are permanent redirects; they differ in method and body handling. 301 historically let clients turn a POST into a GET (most browsers do), while 308 explicitly requires preserving the method and body. Use 308 for a permanent API migration and 301 for a domain change on pages.
How do I tell 502 from 504 quickly?
Check whether the backend is alive. 502 Bad Gateway means the gateway got an invalid response — the process crashed, the port is not listening, the reply was malformed. 504 Gateway Timeout means it never got a response — the backend is running but slow or hung. Look at processes and ports for the first, slow queries and locks for the second.
Is 418 a real status code?
It comes from RFC 2324, the Hyper Text Coffee Pot Control Protocol — an April Fools' RFC from 1998 — so strictly it is not part of core HTTP. Most servers and frameworks will return it, and many sites use it for easter eggs, but do not use it for business meaning in production APIs.