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.
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.
WebPagetest - Run a free website speed test from multiple locations around the globe using real browsers...
OnlineOrNot - Uptime monitoring for software teams (even teams of one).