Source: https://uptimeify.io/resources/platform-and-support/glossary/uptime

# Uptime

> Uptime is the percentage of time a service is available and responding correctly over a given period.

Uptime is the headline reliability metric for any website, API, or server. It is expressed as a percentage: for example 99.9%, which allows roughly 43 minutes of [downtime](/resources/platform-and-support/glossary/downtime) per month. The remaining fraction is downtime.

Uptime is measured by repeatedly checking a service from one or more locations and recording whether each check succeeded. Because a single failed check can be a false alarm, robust monitoring confirms an outage from multiple locations before counting it against uptime.