HTTP Status Codes Explained: 200, 301, 404, 500 and More
A plain guide to the most common HTTP status codes, how the five classes work and how to tell similar codes apart.
The five classes
The first digit tells you the class. 1xx codes are informational, 2xx mean success, 3xx are redirects, 4xx are client errors and 5xx are server errors. Most of the time that digit alone tells you who needs to fix the problem.
Codes you will see most
200 OK means the request worked and 201 Created means a new resource was made. 301 and 308 redirect permanently, while 302 and 307 redirect temporarily. 404 Not Found means the resource is missing, and 500 Internal Server Error is a generic server failure.
Codes that are easy to mix up
401 means authentication is missing or failed, while 403 means the server understood you and still refuses. 301 is permanent and 302 is temporary. 502 means a gateway got a bad reply from upstream, 503 means the service is overloaded or down, and 504 means the upstream did not answer in time. 429 means you are being rate limited.
Look one up
Open the HTTP Status Codes tool, type a number, name or keyword such as 404 or redirect, and filter by class with the 1xx to 5xx buttons. It lists 28 commonly used codes as a quick reference, not the full registry.
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