Frequently Asked Questions
Everything you need to know about the HTTP Status Codes reference.
What are HTTP status codes?
Three-digit codes returned by a server with every HTTP response, indicating whether the request succeeded, failed, or requires further action.
What do the five classes mean?
1xx is informational (request received), 2xx is success, 3xx is redirection, 4xx is a client-side error, and 5xx is a server-side error.
How do I look up a specific code?
Type the number or a keyword into the search box and the matching code appears immediately; you can also filter by class using the tab buttons.
Can I link directly to a code?
Yes — every code has a stable URL fragment (e.g. /dev/http-status-codes#404) you can bookmark or share.
Does it include unofficial codes like 418?
Yes. Widely-used unofficial and extended codes (418, and others) are included and marked with a badge.
Which specification does this follow?
The primary reference is RFC 9110 (HTTP Semantics), with additional codes from WebDAV (RFC 4918) and common unofficial extensions.
What's the difference between 301 and 302?
301 is a permanent redirect (clients and search engines should update the URL); 302 is temporary (the original URL remains canonical).
When should an API return 400 vs 422?
400 (Bad Request) covers malformed syntax; 422 (Unprocessable Content) means the syntax is valid but the server can't process the semantics — common in REST APIs for validation errors.
Is any data sent to a server?
No. All status code data is bundled into the page; nothing is fetched at runtime and nothing you type is transmitted anywhere.
Does it work on mobile?
Yes, fully responsive; the search, filters, and code list fit any screen without overflow.