AppBeat is reliable website monitoring service that alerts you when there is a downtime or failure. It also measures performance and provides functional tests…

Monitis is a web performance monitoring platform.

Pingdom helps you give your customers the best possible web experience by offering a Powerful Web Performance Monitoring Solution.

Port Monitor is an easy tool that does website and server monitoring 24/7 every 60 seconds for free.

StatusCake delivers accurate global website monitoring for tens of thousands of customers.

Zabbix is enterprise open source monitoring software for networks and applications.

Datadog is a monitoring service for cloud-scale applications, bringing together data from servers, databases, tools, and services to present a unified view of…

Nagios known as Nagios Core, is a free and open source computer-software application that monitors systems, networks and infrastructure.

Pingoscope is a website monitoring site.

Site Down is a site downtime monitoring platform.

UptimeRobot is a free website uptime monitoring service.