As of May 2015, Browsermob is dead.
"Website monitoring for the masses. From basic free plans to enterprise level solutions, BrowserMob has it all - try our FREE website monitoring performance test.".
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Uptime.com Alternatives
Uptime.com is described as 'Real-time website monitoring with every-minute checks, global locations, detailed uptime and performance reporting, customizable alerts, and incident detection' and is a Uptime Monitor service in the network & admin category. There are more than 100 alternatives to Uptime.com for a variety of platforms, including Web-based, SaaS, Windows, Self-Hosted and Linux apps. The best Uptime.com alternative is Uptime Kuma, which is both free and Open Source. Other great apps like Uptime.com are Better Stack, UptimeRobot, Kener and Pingdom.