uBlock Origin - Popular and efficient blocker for Chromium, Chrome, Edge, Firefox, Opera, Safari, Thunderbird.
Pingdom - With website monitoring from Pingdom you will be the first to know when your website is down. No installation required. 30-day free trial.
NoScript - NoScript for Firefox pre-emptively blocks malicious scripts and allows JavaScript, Java and other potentially dangerous content only from sites you trust. Download it now for free! - what is it?
StatusCake - Website Uptime Monitoring & Alerts – Free Unlimited Downtime Monitoring
uMatrix - uMatrix: A point-and-click matrix-based firewall, with many privacy-enhancing tools.
Better Uptime - We call you when your website goes down