Glossary · Monitoring

Alert (Monitoring)

A monitoring alert is an automatic notification sent when a check or metric crosses a defined condition, such as a site failing to respond.

Updated October 6, 2026

An alert is a notification generated when a monitoring system decides that a condition needs human attention. The condition might be a failed HTTP check, an error rate above a threshold, or an expiring certificate. Alerts are delivered by email, SMS, push, chat message, phone call or a paging service.

Why it matters

Monitoring that nobody sees is only a record. Alerts close the loop between detection and response, so the time between a failure and a person acting on it is short. Quality matters more than quantity: every alert should be urgent, actionable and clear about what is wrong. Alerts that fail those tests train people to ignore them.

Example

[CRITICAL] shop.example.com
HTTP check failed from 3 of 3 locations
Status: 503 Service Unavailable, started 09:12 UTC
Runbook: https://wiki.example.com/runbooks/shop-503

This includes what, where, since when and what to do next.

Common mistakes

  • Alerting on every anomaly instead of conditions that need action.
  • Sending everything to one shared inbox no one watches.
  • Omitting context such as affected service, severity and a link to a runbook.
  • Firing on a single failed check instead of confirming from several locations.

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