HTTP status codes
Look up an HTTP code: meaning and when to use it.
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The HTTP code dictionary, a search away
When a web request fails, the server returns a three-digit code. This tool gathers and explains them: type a number (404) or a phrase (“not found”), filter by class, and read each code’s meaning and proper use.
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Search
By number, by phrase, or by class (“4” for the 4xx).
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Read the card
Code, official phrase, category and description.
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Pick the right code
For your API, redirect or error page.
The four big families
| Class | Meaning | Examples |
|---|---|---|
| 2xx | Success | 200 OK, 201 Created, 204 No Content |
| 3xx | Redirection | 301 Moved, 302 Found, 304 Not Modified |
| 4xx | Client error | 400, 401, 403, 404, 429 |
| 5xx | Server error | 500, 502, 503, 504 |
Debugging reflex: the first digit tells you the side. A 4xx is to fix on the request (URL, rights, format); a 5xx on the server (code, configuration, overload).
Frequently asked questions
What do the 2xx, 3xx, 4xx, 5xx classes mean?
The first digit gives the category: 2xx = success, 3xx = redirection, 4xx = client-side error (your request), 5xx = server-side error. A glance at the first digit already tells you whose problem it is.
What’s the difference between 401 and 403?
401 (Unauthorized) means “identify yourself”: authentication is missing or failed. 403 (Forbidden) means “I know who you are, but you’re not allowed”. The first is fixed by logging in, the second is not.
When do I use 301 rather than 302?
301 (Moved Permanently) for a definitive move: search engines transfer ranking to the new URL. 302 (Found) for a temporary move: the old URL stays the reference. Getting it wrong hurts SEO.
Does code 418 really exist?
Yes! 418 “I’m a teapot” comes from a 1998 April Fools’ joke (a coffee-pot protocol). It has no serious use but became a cult joke, and some servers return it for silly requests.