HTTP Status Code Lookup
Type a code or keyword to filter the full list of standard HTTP status codes, and click any entry for details on when it appears and how to fix it.
62 standard status codes
1xx — Informational
Interim responses; the request was received and processing continues.
2xx — Success
The request was received, understood, and accepted.
3xx — Redirection
Further action is needed, usually following a new URL.
4xx — Client Error
The request is at fault; fix it on the client side.
5xx — Server Error
The server failed on a valid request; fix it on the server side.
Covers all status codes in the IANA registry. Searching runs entirely in your browser — nothing you type is sent anywhere.
How it works
- Type a status code like 404 or a keyword like “redirect” into the search box — the list filters instantly as you type.
- Scan the grouped results: 1xx informational, 2xx success, 3xx redirection, 4xx client errors, 5xx server errors.
- Click any code to expand a longer note explaining when you typically see it and what to do about it.
Frequently asked questions
- What is the difference between 4xx and 5xx status codes?
- 4xx codes mean the client did something the server rejects — a bad URL, missing authentication, or malformed data — so the fix is on the request side. 5xx codes mean the server itself failed while handling a valid-looking request, so the fix is on the server, its upstream services, or its configuration. This distinction is the first thing to check when debugging any failed HTTP call.
- What is the difference between 401 Unauthorized and 403 Forbidden?
- 401 means the server does not know who you are: credentials are missing, expired, or invalid, and sending correct ones should fix it. 403 means the server knows exactly who you are and still refuses — your account simply lacks permission for that resource. Retrying a 403 with the same credentials will never succeed; you need different permissions or a different account.
- When should I use a 301 redirect versus a 302 or 307?
- Use 301 (or 308 to preserve the request method) when a URL has moved permanently — browsers cache it and search engines transfer ranking signals to the new address. Use 302 or 307 for temporary moves like maintenance pages or A/B routing, since clients keep requesting the original URL. Choosing 301 by accident is painful because browsers cache it aggressively and users may be stuck on the old redirect for a long time.
- Does this lookup tool send my searches anywhere?
- No. The complete status code database is embedded in the page itself, and searching just filters that local list with JavaScript. Nothing you type is sent over the network, logged, or stored, and the tool keeps working even if you go offline after the page loads.
- Are non-standard codes like 418 or 451 real HTTP status codes?
- Yes, both are officially registered. 418 “I’m a teapot” started as an April Fools RFC but is returned by some real servers as an easter egg or as a soft block for automated traffic. 451 “Unavailable For Legal Reasons” is a serious code introduced in RFC 7725 for content removed due to legal demands. Codes you may see in the wild that are not standard, like Nginx’s 499, are vendor-specific and intentionally excluded from official lists.
About this tool
This is an instant reference for every standard HTTP status code, from 100 Continue to 511 Network Authentication Required. The full list is grouped into the five classes — informational, success, redirection, client error, and server error — with the official name and a short practical explanation next to each code. A search box at the top filters the list as you type, so entering 404 or the word “timeout” takes you straight to the relevant entries without scrolling through a spec.
Everything runs client-side: the code database is embedded in the page, and filtering is plain JavaScript over that local data, so no request leaves your browser and lookups are instantaneous. Clicking any code expands a longer note that covers the two things documentation usually skips — the real-world situations where the code shows up, and the concrete first steps to fix or handle it, whether the problem is on the client or the server.
The tool is aimed at the moments developers actually reach for a status code reference: deciding what an API endpoint should return for a failed validation (400 or 422?), debugging a 502 from a reverse proxy, working out why a browser keeps following an old 301, or explaining to a teammate why retrying a 403 is pointless. It also covers the codes people half-remember, such as 409 Conflict for concurrent edits, 429 Too Many Requests for rate limiting, and 304 Not Modified for cache revalidation.
A practical tip when debugging: always check the response class first. A 4xx tells you to inspect the request — URL, method, headers, body, and credentials — while a 5xx tells you to look at server logs and upstream dependencies. And remember that status codes are only the machine-readable summary; well-designed APIs pair them with an error body that explains the specific failure, so read both before changing any code.