HTTP Status Code Reference

The HTTP Status Code Reference is a searchable cheat sheet covering the 26 most commonly used status codes across the five classes: 1xx informational, 2xx success, 3xx redirection, 4xx client error and 5xx server error. Each entry has the standard name and a one-sentence explanation. It is static reference material, not a diagnostic tool. It does not request any URL, cannot tell you why a particular site returned a 404, and does not include every standard status code.

How to use it

1. When the page opens, all 26 codes are listed in ascending order, with the number coloured by class.
2. To find one quickly, type into the search box at the top. You can enter a number (404, or just 40 to see every 40x), or part of the name (such as timeout).
3. The list filters as you type. Each entry shows the code, its name and a short description.
4. If nothing matches, the page shows "No matching status codes found". Clear the box to see the full list again.

Example lookups

Say you see a 502 while testing an API. Type 502 and you get "Bad Gateway": a server acting as a gateway or proxy received an invalid response from the upstream server. Type 504 and you get "Gateway Timeout": the gateway did not get a timely response from upstream. Comparing the two helps you tell whether upstream answered badly or did not answer in time. Searching 30 matches 301, 302, 304, 307 and 308, so you can see that 301 is a permanent move, 302 is temporary, and 304 tells the browser to use its cached copy.

Codes included

• 1xx informational: 100 Continue, 101 Switching Protocols.
• 2xx success: 200 OK, 201 Created, 204 No Content, 206 Partial Content.
• 3xx redirection: 301 Moved Permanently, 302 Found, 304 Not Modified, 307 Temporary Redirect, 308 Permanent Redirect.
• 4xx client error: 400 Bad Request, 401 Unauthorized, 403 Forbidden, 404 Not Found, 405 Method Not Allowed, 408 Request Timeout, 409 Conflict, 410 Gone, 418 I'm a teapot, 422 Unprocessable Content, 429 Too Many Requests.
• 5xx server error: 500 Internal Server Error, 502 Bad Gateway, 503 Service Unavailable, 504 Gateway Timeout.

Supported features and known limits

• Only the 26 codes above are included. Others, such as 451, are not available, and searching for them shows no match.
• Search matches the code number, the name (the Chinese name is also matched) and the description text, so words such as cache or rate-limited will find the matching code.
• Number search is a substring match, so typing 4 lists every code containing a 4, including 204, 304, 404 and 504.
• Each description is one sentence. It does not cover response headers, caching rules, or SEO and browser behaviour. For exact behaviour refer to RFC 9110 and to the server or framework you use.
• The page makes no network request to test the status code of any URL.

What is the difference between 401 and 403?

401 means authentication is required and you either did not provide credentials or they were invalid. 403 means the server understood the request, you may even be logged in, but it still refuses, usually because of insufficient permissions. In short, 401 is not logged in or invalid login, and 403 is logged in but not allowed.

How do 301 and 302 redirects differ for search engines?

A 301 says the resource has moved permanently, and search engines generally transfer the old address's standing to the new one over time. A 302 says the move is temporary, and the old address is usually kept. The exact effect depends on how each search engine treats them. This page only lists the standard meaning of the two codes.

How do I tell 500, 502, 503 and 504 apart?

500 means the server itself hit a situation it could not handle. 502 means a gateway or proxy got an invalid response from upstream. 503 means the server is temporarily unable to handle the request, often due to overload or maintenance. 504 means the gateway did not get a response from upstream in time. The last three typically appear in setups with a reverse proxy or load balancer.

Why can't I find 451?

Because the page currently includes only 26 common codes, and anything outside them cannot be found. For a complete list, check RFC 9110 or the IANA HTTP status code registry.

Privacy and how your data is handled

The data is built into the page code and the filtering happens in your browser. The keywords you type are not sent to a server or stored.