The Complete Glossary of Uptime Monitoring Terms
A plain-English glossary of uptime monitoring terms, including availability, SLA, SLO, synthetic monitoring, MTTR, MTTD, status pages, and alert fatigue.
Availability
Availability describes whether a service is usable when customers need it. It is often expressed as an uptime percentage, such as 99.9% availability.
Uptime monitoring
Uptime monitoring checks whether a website, API, or service is reachable and responding correctly. Strong uptime monitoring may include HTTP checks, SSL monitoring, domain monitoring, API monitoring, and synthetic transactions.
Synthetic monitoring
Synthetic monitoring runs scripted tests that simulate user workflows. Examples include login, checkout, search, API calls, and form submission.
SLA, SLO, and SLI
An SLA is a customer-facing service level agreement. An SLO is an internal reliability target. An SLI is the metric used to measure the target, such as successful requests or synthetic check success.
MTTD and MTTR
MTTD means mean time to detect. MTTR means mean time to resolve. Together they show how quickly a team notices and fixes incidents.
Status page
A status page communicates current service health, incident updates, maintenance, and uptime history to customers.
Alert fatigue
Alert fatigue happens when teams receive too many noisy or low-value notifications. It reduces trust in monitoring and can slow incident response.
Incident response
Incident response is the process of detecting, triaging, communicating, resolving, and learning from production problems.
Error budget
An error budget is the amount of unreliability a service can tolerate while still meeting its reliability target. It helps teams balance shipping speed and uptime.