Website Uptime Checker

Our checker sends an HTTP HEAD request to your domain over HTTPS (falling back to HTTP) and measures the response time. It reports the HTTP status code, whether the server is reachable, and how quickly it responds. A status code below 500 is considered online.

HTTP 200 OK means the server received the request and returned a successful response. Your site is online and reachable. 3xx codes indicate redirects, 4xx indicate client errors (like 404 Not Found), and 5xx indicate server errors.

Under 300ms is excellent, 300-800ms is good, 800-2000ms is fair, and over 2000ms is slow. Slow response times increase bounce rates significantly — studies show 53% of mobile users abandon pages that take over 3 seconds to load.

This tool performs a one-time check from our server. On paid plans, CertNotify monitoring repeats a similar check once a day: one HEAD request to each monitored site, and if the site does not answer or returns a server error, you get an email alert, or one in Slack and the other channels in your alert settings. Because it is a daily check, an outage that starts and ends between two checks is not seen. For minute-by-minute downtime alerts, use a dedicated uptime monitor alongside it.

Your site may block server-to-server HEAD requests, use IP-based access restrictions, require JavaScript to load (SPAs), or be behind a CDN/WAF that blocks automated requests. Try checking a specific resource URL or ensure your site accepts requests from external servers.