Uptime Kuma - A fancy self-hosted monitoring tool.
PageSpeed Insights - PageSpeed is addon for ...
Statsignal - Statsignal is a simple and cost-effective way to monitor your website or server and publish a status page of your system.
GTmetrix - GTmetrix is a free tool that analyzes your page's speed performance. Using PageSpeed and YSlow, GTmetrix generates scores for your pages and offers actionable recommendations on how to fix them.
UptimeRobot - Free Website Uptime Monitoring
CheckPageSpeed.com - Website Speed and Performance Analyzer