Monitor
Uptime monitoring, SSL certificate checks, and network path tracing — free tools to catch problems before your users do.
Keeping an eye on things
Monitoring tools watch something over time, or check it right now, so problems surface before your users notice them. That might mean an uptime check running every few minutes, a certificate expiry date you'd otherwise forget about, or tracing the network path a request takes to see where it slows down.
The common thread is visibility — knowing the current state of a system without having to check it by hand.