uptime monitoring
Periodically probing a URL or endpoint from an external location to detect outages and degraded performance.
Uptime monitoring is the practice of regularly checking a service — typically over HTTP, but sometimes over TCP, ICMP, or a custom protocol — from one or more external locations to verify that it is responsive. The result of each check is a pass/fail plus a latency measurement.
The fundamental value of uptime monitoring is that it asks “is the service responsive to the outside world?” from outside the service’s own perimeter. An internal health check can pass while customers are unable to reach the site at all — DNS failures, expired certificates, misconfigured firewalls, and CDN outages all break customer experience while internal metrics look healthy.
Modern uptime monitoring is also a feedback loop into alerting and on-call: when checks fail in a defined pattern (e.g. three consecutive failures from two regions), the tool wakes a human up so they can investigate.
uptime
The proportion of time a service is reachable and responding correctly, usually expressed as a percentage over a window.
downtime
Any period during which a service is unavailable or degraded for end users. The inverse of uptime.
synthetic check
An automated, scripted interaction with a service that simulates real user behaviour and runs on a schedule.
incident
A discrete event during which a service was unavailable or degraded, with a defined start, updates, and resolution.