The trade-off in one line
UptimeRobot checks your sites from its own servers, so if your entire network goes down, you still get alerted, because the monitor isn't sitting inside your own infrastructure. Uptime Kuma runs wherever you put it, which means it's free forever and fully under your control, but if the server hosting Kuma goes offline along with the thing it's monitoring, you get silence instead of an alert. That single architectural difference should decide which one you pick before price does.
UptimeRobot pricing
UptimeRobot's current plans, billed annually:
The free plan alone covers most personal projects and small sites: 50 monitors is enough for a handful of services plus their SSL certificates and DNS records. The paid tiers exist mainly to buy a faster check interval and status pages, not to unlock monitoring that's otherwise missing.
Uptime Kuma, the cost of "free"
Uptime Kuma is built by Louis Lam and released under the MIT license, with no paid tier at all. It runs as a Docker container or a Node.js process on a server you control, most commonly a small VPS. There's no monitor limit built into the software; the only ceiling is what your server's CPU and network connection can handle.
The real cost isn't money, it's maintenance. You're responsible for keeping the container updated, backing up its database, and making sure the server itself has enough uptime to be a reliable witness for everything else. If you already run a VPS for other things, adding Kuma costs nothing extra. If you don't, you're taking on server administration specifically to save a monitoring subscription that might cost less than the VPS itself.
Feature differences beyond price
UptimeRobot includes hosted status pages, phone call and SMS alerts, and integrations like Zapier and PagerDuty out of the box on paid tiers, all without you running anything. Uptime Kuma supports a wide range of notification channels through its own integrations (Telegram, Discord, Slack, email, and dozens more via community-maintained providers) but status pages and everything else run on your server, so they inherit that server's uptime.
Kuma also monitors things a purely external service can't easily reach: internal services on a private network, local Docker containers, or anything behind a firewall with no public endpoint. UptimeRobot, checking from the outside, is blind to those by design.
Frequently asked
Is Uptime Kuma really free?
Yes, Uptime Kuma is free, open-source software released under the MIT license. There's no paid tier and no monitor cap in the software itself; the only cost is the server you run it on.
Does UptimeRobot have a free plan?
Yes, UptimeRobot's free plan covers up to 50 monitors checked every 5 minutes, with no credit card required. Paid plans start at the Solo tier for faster 60-second checks and more features.
Do I need a server to run Uptime Kuma?
Yes. Uptime Kuma is self-hosted software, typically run as a Docker container, so you need a VPS or home server with a public network path to whatever you're monitoring. UptimeRobot needs none of that since it runs on UptimeRobot's own infrastructure.