How it works

1. Every minute a Cloudflare Cron Trigger wakes the checker. Monitors are split into shards, and each shard checks only the monitors that are due, in parallel.
2. Each check is an HTTP GET with a 10-second timeout that follows up to 5 redirects. Status 200–399 is up. Keyword monitors read up to 1 MB of the response.
3. A failure is confirmed with a second check a few seconds later. Then an incident opens and alerts go out. The first successful check closes it.
4. Results (status, response time, daily uptime) are stored in a Durable Object and kept for 90 days.
5. Safety: only public http(s) URLs on ports 80, 443, 8080 or 8443 can be checked. Private, local and reserved addresses are refused, including hostnames that resolve to them and redirects that point to them.