Moonitor
Uptime monitoring for a one-off price on AppSumo: 20 monitors at 60-second checks, SSL checks, all alert channels and branded status pages.
Updown.io
Pay-as-you-go website monitoring with no subscription: buy credits, check every 15 seconds to every hour, and get SSL and domain expiry alerts.
Upptime
Free, open-source uptime monitor and status website that runs on GitHub, checking your pages every 5 minutes. It needs a GitHub repository.
Uptime Kuma
Free, open-source uptime monitor and status pages that you host yourself, with checks as often as every 20 seconds and 90+ alert services.
StatusCake
Free website uptime checks for personal sites: 3 monitors at 15-minute checks with email alerts. The free account is for personal use only.
Cronitor
Cron job and heartbeat monitoring, plus website and API checks, on a free plan for small projects: 5 monitors, email and Slack alerts.
Checkly
Developer monitoring on a free Hobby plan: 10 uptime monitors at 2-minute checks plus API checks and scripted Playwright browser checks each month.
Instatus
A status page with uptime monitoring built in: 15 monitors at 2-minute checks and a public page for up to 200 subscribers, free with no card.
Site24x7
Free forever website monitoring for 50 sites at 5-minute checks, with SSL certificate expiry checks, a public status page and uptime reports.
Better Stack
Uptime checks, cron heartbeats and a status page on a free plan for personal projects, with Slack and email alerts. Paid plans add on-call tools.
Hyperping
Free uptime and SSL monitoring for 20 checks from 18 regions, with email, Slack and Teams alerts and a basic status page. No card needed.
Pulsetic
Free monitoring for 10 sites, APIs, cron jobs or domains, with SSL checks, domain expiry reminders and 3 status pages. No card needed.
UptimeRobot
Watch up to 50 sites, ports or cron jobs free, checked every 5 minutes, with email and chat alerts and a status page. No card needed.
HetrixTools
Free uptime monitoring for 15 sites at 1-minute checks, with SSL expiry, domain expiry and nameserver-change alerts plus a public status page.