Events
A channel is told about a change of state, never about a single failed check:
- Down, and Up again after a down.
- Blocked by a firewall or a Cloudflare challenge, and no longer blocked (per channel, on by default).
- Partial: unreachable from some continents only, and reachable everywhere again. Off unless the monitor's Alert on partial outages is on.
- Slow, and normal speed again. Off unless the monitor's Alert when it turns slow is on.
- Heartbeat missed: a heartbeat monitor whose job did not call in, or called
/fail. - Domain expiring: 30, 14, 7 and 1 days before a domain of one of your monitors expires, and on the day.
- Credits running low, sent to the account's channels.
A monitor whose state was unknown or unconfirmed and becomes up sends nothing, so a new monitor does not announce itself. Pausing, resuming and maintenance windows send nothing. A certificate about to expire is shown as a warning in the panel and is not alerted; an expired certificate is an outage.
The message
The subject or title is <State>: <monitor name>, for example Down: shop.example.com or Still down: shop.example.com for a reminder. The body carries the target, the reason and its detail, "confirmed from N locations on K continents at
On accounts where AI explanations are turned on, the down alert also carries a short explanation of the evidence, written by Claude from the probe results; the alert waits up to 45 seconds for it. See AI explanations.
Delays and reminders
Each channel has its own delay (immediately, or after 2 to 60 minutes down) and its own reminder rhythm (none, every 5 minutes to every 4 hours, at most 15 per outage). An outage that ends inside the delay is never reported to that channel. So a Slack channel can hear about everything at once while PagerDuty is paged only after ten minutes. Putting an incident on hold on the Incidents page pauses the reminders of every channel while someone works on it; they resume when it is taken off hold, and the recovery alert is sent as usual.
Grouped alerts
When three or more monitors in the same group change state together within a minute, the channel gets one message, "N sites on group.<kind>.
Audience regions
A monitor can be told where its visitors are (for example Europe and North America) so that partial and slow are judged on the probes that matter to them. The setting is per monitor, with an account default; a reseller's default applies to its customers' monitors.
Last change: 31 October 2026.