The best free alternative to Pingdom is Better Uptime. If that doesn't suit you, our users have ranked more than 100 alternatives to Pingdom and loads of them is free so hopefully you can find a suitable replacement. Other interesting free alternatives to Pingdom are Freshping (Free), UptimeRobot (Freemium), StatusCake (Freemium) and PHP Server Monitor (Free, Open Source).
All of your MX record, DNS, blacklist and SMTP diagnostics in one integrated tool. Input a domain name or IP Address or Host Name. Links in the results will guide you to other relevant tools and information.
Pingbreak is an original and free monitoring service. Get notified through Twitter if your website is down. Pingbreak checks all of your websites each minute and alert you instantly by Direct Message (DM).
GitHub-powered open-source uptime monitor and status page. Monitor uptime every 5 minutes Using GitHub Actions, monitor unlimited webpages every 5 minutes, and store version-controlled response time stats.