Activity Monitor is a utility application included on every Mac since Mac OS X 10.3 Panther. Essentially a task manager, the application enables users to monitor their Mac’s CPU processes, RAM usage and more.
Users can also use Activity Monitor to quit rogue applications or those leaking memory. Though it is an incredibly useful asset to nearly any Mac user, it has unfortunately been banished to the Utilities folder and therefore is seldom opened by the average user.
What many Mac users—even those familiar with the app—might not realize is that Activity Monitor’s functionality extends beyond its single window design. The application’s cardiac monitor styled icon—which has always been a personal favorite of mine—conceals an active icon capable of displaying your Mac’s performance or resource usage in real time.
To enable this hidden feature, simply navigate to Applications > Utilities > Activity Monitor and launch the application. Once the app is running, right click its icon in the dock and select Dock Icon. The resulting menu presents a number of system monitoring options that will replace the app’s default icon as long as it’s running.
Users can select from CPU Usage, CPU History, Network Usage, Disk Activity and Memory Usage. Although the icon will revert to its original form upon quitting the app, you can always keep Activity Monitor in your dock for quick, convenient access.