Explainer1 min readUpdated July 1, 2026

HTTP status codes explained

Short answer

An HTTP status code is a three-digit number a server returns to describe the outcome of a request. The first digit sets the category: 2xx success, 3xx redirect, 4xx client error, 5xx server error. So 404 means the client asked for something that does not exist.

The five groups

Every status code belongs to a group set by its first digit. Knowing the group tells you who is responsible — the request, a redirect, the client, or the server — before you read the exact code.

1xx Informational — request received, still processing (rare)
2xx Success — the request worked (200 OK, 201 Created, 204 No Content)
3xx Redirect — go somewhere else (301 Moved, 302 Found, 304 Not Modified)
4xx Client error — the request was wrong (400, 401, 403, 404, 429)
5xx Server error — the server failed (500, 502, 503, 504)

Codes you meet most

200 OK — standard success
301 Moved Permanently — the URL changed for good; update links
404 Not Found — the resource does not exist at that URL
403 Forbidden — you are not allowed, even if authenticated
401 Unauthorized — you need to authenticate first
429 Too Many Requests — you hit a rate limit; slow down
500 Internal Server Error — the server crashed handling the request
503 Service Unavailable — the server is temporarily down or overloaded

Try it: HTTP Status LookupLook up any status code and its meaning instantly.Open tool

404 vs 410, 301 vs 302404 means not found (may return later); 410 means gone for good. 301 is a permanent redirect (SEO passes to the new URL); 302 is temporary. Choosing the right one matters for search engines.

The code travels in the response's status line, alongside the headers. See what is an HTTP header. For the full list, see the HTTP status codes reference.

References

Questions

What does a 404 error mean?

404 Not Found means the server could not find anything at the requested URL. The request was valid, but the resource does not exist there — often a broken link or a mistyped address.

What is the difference between a 4xx and a 5xx error?

A 4xx code means the client's request was at fault (bad URL, missing auth, too many requests). A 5xx code means the server failed while handling an otherwise valid request.

Is 200 the only success code?

No. 200 OK is the most common, but 201 Created, 202 Accepted, and 204 No Content are also successes. Any 2xx code means the request succeeded.

Does this send my data anywhere?

No. Utilumo's developer tools parse and transform input inside the browser tab. Nothing is uploaded, stored, or logged.