HTTP Status Codes Reference
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A searchable reference of every HTTP status code from 1xx to 5xx, each with its official name and a plain-English description. Type a number or keyword to filter the list instantly. Everything runs in your browser.
How HTTP status codes are organised
Every HTTP response carries a three-digit status code that tells the client, in a standard way, what happened. The first digit sets the class, so you can understand a response at a glance even without memorising the exact code. This reference lists them all with names and plain-English descriptions, and filters as you type.
The five classes are informational (1xx), success (2xx), redirection (3xx), client errors (4xx) and server errors (5xx). Knowing the class immediately narrows down whether a problem is on the client side, the server side, or simply a redirect doing its job.
- 1xx Informational — the request was received and the process continues.
- 2xx Success — the request was received, understood and accepted.
- 3xx Redirection — further action is needed to complete the request.
- 4xx Client Error — the request has bad syntax or cannot be fulfilled.
- 5xx Server Error — the server failed to fulfil a valid request.
The codes you will meet most often
A handful of codes cover the vast majority of real traffic. 200 OK is the everyday success response. 301 and 302 handle permanent and temporary redirects, and 304 Not Modified lets caches skip re-downloading unchanged resources. On the error side, 400 signals a malformed request, 401 and 403 separate 'not authenticated' from 'not allowed', and 404 marks a missing resource.
Server-side, 500 is the catch-all internal error, while 502, 503 and 504 point at gateway, availability and upstream-timeout problems — often the difference between 'the app crashed' and 'the app is fine but something behind it is not'. Distinguishing them saves real debugging time.
The subtler distinctions worth knowing
Several codes are frequently confused. 401 Unauthorized actually means unauthenticated — you have not proven who you are — whereas 403 Forbidden means you are known but still not permitted. Sending the wrong one leaks or hides information about your endpoints.
Among redirects, 301 versus 302 matters for SEO and caching: 301 tells clients the move is permanent and safe to remember, while 302 keeps the original URL authoritative. And 307/308 exist specifically to preserve the request method during a redirect, unlike the older 302/303 which historically let clients switch to GET.
APIs lean on a few extras too: 422 Unprocessable Content for validation failures, 429 Too Many Requests for rate limiting, and 451 for content withheld for legal reasons. This searchable list keeps all of them one keystroke away.
Frequently asked questions
What is the difference between 401 and 403?
401 Unauthorized means you are not authenticated — credentials are missing or invalid. 403 Forbidden means you are authenticated but not permitted to access the resource.
When should I use 301 versus 302?
Use 301 Moved Permanently when a URL has changed for good, so clients and search engines update their references. Use 302 Found (or 307) for a temporary redirect where the original URL should stay authoritative.
What does 429 mean?
429 Too Many Requests indicates rate limiting — the client has sent too many requests in a window of time. Responses often include a Retry-After header telling you when to try again.
Is 418 a real status code?
418 I'm a Teapot comes from an April Fools RFC and is not meant for real use, though it is officially reserved and some services return it as a joke or a honeypot signal.
What causes a 502 versus a 504?
Both involve a gateway or proxy. 502 Bad Gateway means it received an invalid response from an upstream server; 504 Gateway Timeout means the upstream server did not respond in time.
Does this reference cover WebDAV and newer codes?
Yes. It includes WebDAV codes like 207 and 423, plus modern additions such as 103 Early Hints, 425 Too Early and 451 Unavailable For Legal Reasons.
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