HTTP Status Codes
HTTP status code reference with likely causes and where to look
What is HTTP Status Codes?
A searchable HTTP status code reference grouped from 1xx to 5xx, giving the meaning of each code along with the causes that usually produce it and where to start debugging. You can search by number or keyword, and because the data ships with the page, every lookup is local.
How to use HTTP Status Codes
- 1Type a status code or a keyword into the search box, such as 502, timeout, or CORS.
- 2Filter by class to narrow quickly to 4xx client errors or 5xx server errors.
- 3Expand an entry to read the meaning, the common causes, and suggested next steps.
- 4When debugging a live incident, read the code alongside your application and gateway logs.
Frequently asked questions
What is the difference between a 502 and a 504?+
502 Bad Gateway means the gateway received an invalid response from upstream, typically because the upstream process crashed or returned a malformed message. 504 Gateway Timeout means the gateway gave up waiting: upstream is alive but too slow. Chase a crash for the first and slow queries or timeout settings for the second.
Should my API return 401 or 403?+
Return 401 Unauthorized when the caller is unauthenticated or the credentials are invalid, signalling that they should log in or refresh their token. Return 403 Forbidden when the identity is established but lacks permission, where signing in again changes nothing. Blurring the two leaves clients unable to decide what to do next.
Why do I get a 200 response when the request actually failed?+
That usually means the business error is wrapped inside a 200 response body. The pattern breaks caching, monitoring, and retry logic, which all key off the status code. Let the HTTP status describe the transport and request layer, and keep domain-level error codes in the body so the two stay semantically separate.
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