Down for everyone, or just you?
If a site loads here but not for you, the problem is usually local: your network, DNS cache, VPN, a browser extension or a firewall. If it fails here too, the site itself is down or misconfigured.
The check resolves DNS, fetches the page, and reports the status code and time to respond. Status 5xx means the server failed; 4xx means it answered but refused the request.
Questions
Where is the check made from?
From Cloudflare's network, near the request.
Why does a site say 403 here but work for me?
Some sites block automated checks. A 403 means the server is up.
Can I monitor a site?
This is a one-off check. Use an uptime monitor for alerts.
What is a slow response?
Over about 2 seconds to respond is flagged as slow.