What is an uptime monitoring tool?

An uptime monitoring tool is software that continuously checks whether your website, server, or application is reachable, and alerts you the moment it isn't.

Rather than refreshing the browser tab every hour, you let a monitoring service do it for you from servers around the world, every minute or so. When a check fails, the service verifies the problem (ideally from a second location so one flaky network doesn't trigger a false alarm) and pings you through email, Slack, SMS, or whichever channel you actually pay attention to.

Good uptime monitoring also keeps a full history, so you can answer questions like "how much downtime did we have last month?" without guessing.

Oh Dear is one of those tools. We check every minute, verify downtime from a second location, and notify you through more than a dozen channels.