Uptime Kuma

Uptime Kuma checks your services over HTTP, TCP, ping, DNS and more, then alerts you through an enormous list of notification channels — Telegram, Discord, email, webhooks, and dozens of others. Public status pages are built in.

It runs from a single container with a SQLite database and a genuinely pleasant UI, which explains why it became a homelab staple almost overnight. Very large numbers of monitors can strain it; for a few dozen services it is effortless.

The first monitoring tool most self-hosters should install, and often the only one they need.