Site uptime monitoring is the art of keeping track of when your site is down. Basically when you signup for a service that monitors your uptime. What they are really doing is monitoring how much downtime and when your downtime occurs. Different site uptime monitoring services may check every 1 minute to half an hour intervals. When the uptime monitoring service doesn’t get the expected response via HTTP header or a simple ping. The uptime monitoring service may record it as your site being not available aka downtime.