OnlineOrNot's lessons from Cloudflare's outage on 2025-11-18
On 2025-11-18 at 11:48 UTC, Cloudflare declared an incident affecting the global network (that also affected OnlineOrNot). OnlineOrNot monitors websites, APIs, web apps, and cron jobs, while providing status pages as well. While we partially mitigated the issue by enabling a fallback to AWS-based monitoring, between 13:00 UTC and 14:33 UTC failing checks went unreported, heartbeat checks over-reported, and status pages were unavailable.