200: OK
The server successfully handled the request. This is a strong sign the tested page is responding from the checking server's location.
301 and 302: Redirect
The server asks the client to go to another URL. This is normal when a website moves or routes HTTP visitors to HTTPS. Our checker follows up to three redirects after checking that each new destination is a public website. If the final destination cannot be tested safely, we show an unverified redirect instead of claiming the website is up.
401: Unauthorized
The resource requires authentication. The server responded, but access may require a valid login.
403: Forbidden
The server refuses the request. Bot protection, regional restrictions or permissions can cause this result. It doesn't automatically mean the website is down.
404: Not Found
The server was reached, but the requested resource wasn't found. A site's homepage may be missing even when other services are working.
429: Too Many Requests
The server is limiting requests. A checker can receive this response even when the website is generally available to ordinary visitors.
500: Internal Server Error
An unexpected problem occurred on the server while processing the request. The site may be experiencing an outage or application failure.
502, 503 and 504: Gateway / availability problems
These often indicate a backend or proxy problem, temporary service unavailability, or a gateway timeout. Retry later or consult the site's official status updates.
DNS failures, TLS certificate problems and timeouts may produce no HTTP status code at all. Our checker separates those from servers that return an HTTP 4xx or 5xx response.