HTTP Status Codes Reference

Search and browse over 60 HTTP status codes grouped by class, each with its official name and a plain description.

HTTP Status Codes Reference tool

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Example

Input: Search: 404

Result: 404 Not Found - The server cannot find the requested resource. This is the most common error response on the web.

Searching by number or keyword filters the list, and tapping a code expands its description.

The Five Classes of Status Codes

ClassMeaningCodes listedCommon examples
1xxInformational4100 Continue, 103 Early Hints
2xxSuccess10200 OK, 201 Created, 204 No Content
3xxRedirection8301 Moved Permanently, 302 Found, 304 Not Modified
4xxClient error29400 Bad Request, 401 Unauthorized, 403 Forbidden, 404 Not Found, 429 Too Many Requests
5xxServer error11500 Internal Server Error, 502 Bad Gateway, 503 Service Unavailable, 504 Gateway Timeout

Counts are the codes included in this reference (62 in total).

  1. Type a code (such as 404 or 502) or a keyword (such as "redirect" or "unauthorized") into the search bar.
  2. Scroll through the matching codes, grouped into 1xx, 2xx, 3xx, 4xx and 5xx with a count for each class.
  3. Click a code to show its description.
  4. Compare related codes, such as 401 and 403 or 301 and 308, to pick the right one.
  5. Use the copy button to copy the code and name, such as "404 Not Found".

HTTP Status Codes by Class

An HTTP status code is the three-digit number a server sends back with every response to say how a request went. 200 means OK, 301 means the page has moved for good, 404 means not found and 500 means the server hit an error. This reference lists 62 codes with their official names and a plain description, grouped by class.

The first digit tells you the class. 1xx codes are early, in-progress replies. 2xx means success. 3xx means the client must go somewhere else, usually to a new URL. 4xx means the problem is on the client side, such as a bad link or a missing login. 5xx means the server failed even though the request looked fine. So when you see 502 or 504, look at the server or proxy, not at the browser.

Search by number, name or keyword. Typing "timeout" finds 408 Request Timeout and 504 Gateway Timeout, and "redirect" brings up the 3xx group. Tap a code to read its description, then copy it as "404 Not Found" for a bug report or an API spec. Most codes that only apply to WebDAV, a file-sharing extension of HTTP, say so in their descriptions.

Picking the right code matters for SEO and for APIs. Use 301 or 308 when a URL changes for good, so search engines move their signals to the new address, and 302 or 307 for short-term moves. In an API, 400 means the request is malformed, 422 means it is well formed but fails validation, and 429 tells a client to slow down. For the content type to send with a response, see the MIME Types Lookup. To check a URL piece by piece, use the URL Parser.

Sources

Frequently Asked Questions

A 301 says the page has moved for good, so search engines replace the old URL with the new one. A 302 says the move is temporary, so the old URL stays in the index. 308 and 307 mean the same things, but also require the browser to keep the same method, such as POST, when it follows the redirect.
A 401 Unauthorized means the server does not know who you are yet, so you need to log in or send valid credentials. A 403 Forbidden means the server knows who you are, or does not care, and still refuses. Logging in again will not fix a 403. Some sites return 404 instead of 403 to hide that a page exists.
A server in the middle, such as a proxy, load balancer or CDN, tried to reach the application server behind it and got a bad reply or none at all. Common causes are an app that crashed, a wrong port, or a server restarting. Visitors can only wait and refresh. Site owners should check the application logs first.
Both tell search engines the page is not there. A 410 Gone says it was removed on purpose and will not come back, which can get it dropped from search results a little faster. A 404 is fine when you are not sure, or when the page might return. Never return 200 with a "not found" message.
It comes from an April Fools joke, RFC 2324 from 1998, which described a protocol for controlling coffee pots. A teapot asked to brew coffee answers 418. It is not a real error, but some servers and frameworks return it for fun or to reject bots. You should not use it for anything serious in an API.

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