Do You Have a List of IP Addresses I Need to Allow for Monitoring?

Yes. The current list of UptimeRobot's monitoring locations and IP addresses is always kept up to date at https://uptimerobot.com/help/locations/.

That page reflects our current IP addresses, so allowlist directly from it rather than copying the list elsewhere — and re-check it whenever you add or update your firewall rules, since the IPs can change.

If your firewall or WAF can filter by request headers instead of (or in addition to) IP address, you can also identify UptimeRobot's checks by their user-agent string. See What is the UptimeRobot User Agent String? for the exact string to allow.