Uptime
Short definition
Uptime is the percentage of a given period during which a website or server stays reachable without interruption.
Uptime shows what share of a measured period a server or service stayed running and reachable. Providers aim for figures close to a hundred percent, though zero downtime is practically impossible.
Hosting providers usually commit to an uptime figure through a service level agreement, falling below that threshold can trigger compensation. Downtime can come from maintenance, an attack, or hardware failure.
Uptime is tracked by external tools pinging the site at regular intervals; those tools alert the team the moment something goes down, often before a customer notices.
Uptime is often confused with page speed, being reachable does not mean a page loads quickly. A site can be painfully slow and still count as technically up, so most monitoring tools would not flag it as downtime at all, speed is tracked with separate metrics while reachability is what uptime actually measures.
Why it matters
A site with frequent downtime loses trust and sales in the same breath, for anything handling payments or bookings every minute offline is lost revenue. Monitoring uptime means catching the problem before a customer complains.
Illustrative example
A payment provider's monitoring tool caught a brief overnight outage and it was fixed before customers woke up and noticed.
