HTTP Status Code Reference
Every HTTP response status code explained in plain English. Search, filter by category, or jump to a specific code.
What Are HTTP Status Codes?
HTTP status codes are three-digit numbers returned by a web server in response to a client's request. They indicate whether the request was successful, redirected, resulted in an error, or requires further action. Every time your browser loads a page, downloads a file, or submits a form, the server sends back one of these codes along with the response.
Status codes are grouped into five classes based on their first digit. 1xx codes are informational, 2xx codes indicate success, 3xx codes handle redirection, 4xx codes signal client-side errors, and 5xx codes represent server-side errors. Understanding these codes is essential for web developers, DevOps engineers, and anyone debugging web applications or APIs.
The Most Common HTTP Status Codes Explained
- 200 OK — The request succeeded. This is the standard response for successful HTTP requests.
- 301 Moved Permanently — The resource has been permanently moved to a new URL. Search engines transfer ranking to the new URL.
- 302 Found — The resource has been temporarily moved. The client should continue using the original URL for future requests.
- 400 Bad Request — The server could not understand the request due to invalid syntax or missing parameters.
- 401 Unauthorized — Authentication is required. The client must provide valid credentials.
- 403 Forbidden — The client does not have permission to access the resource, even with authentication.
- 404 Not Found — The server could not find the requested resource at the given URL.
- 500 Internal Server Error — A generic error indicating something went wrong on the server side.
- 502 Bad Gateway — The server, acting as a gateway or proxy, received an invalid response from an upstream server.
- 503 Service Unavailable — The server is temporarily unable to handle the request, often due to maintenance or overload.