HTTP Status Codes
Free online HTTP status code lookup tool
Understanding HTTP Status Codes
HTTP status codes are three-digit numbers returned by a server in response to a client request. They are grouped into five categories: 1xx Informational, 2xx Success, 3xx Redirection, 4xx Client Error, and 5xx Server Error. Understanding these codes is essential for web development and API debugging.
Common Status Codes to Know
200 OK — request succeeded. 301 Moved Permanently — resource moved. 304 Not Modified — cached version is valid. 400 Bad Request — malformed request. 401 Unauthorized — authentication required. 403 Forbidden — access denied. 404 Not Found — resource does not exist. 500 Internal Server Error — server crash. 502 Bad Gateway — upstream error. 503 Service Unavailable — server overloaded.
▶What is the difference between 401 and 403?
401 Unauthorized means the request lacks valid authentication credentials. 403 Forbidden means the server understands the request but refuses to authorize it, even with valid credentials.
▶What does a 301 redirect mean for SEO?
A 301 (Moved Permanently) redirect passes most of the link equity (SEO value) to the new URL. It tells search engines to update their index to the new URL.
▶What is the difference between 404 and 410?
404 (Not Found) means the resource does not exist. 410 (Gone) explicitly tells the client the resource was permanently deleted. Search engines treat 410 as a stronger signal to remove the URL from their index.