Apps can affect Mac performance, battery runtime, temperature, and fan activity

You can use Activity Monitor to see whether a Mac app is using more of the CPU than it should.

When an app isn't responding or working correctly, it might use more of the processor (CPU) than it should, even when the app doesn't seem to be doing anything. As the CPU gets busier, it uses more energy, which reduces the length of time that your Mac can run on battery power. It also generates heat, which can cause the fans in your Mac to spin faster. 

Use Activity Monitor to check CPU activity

Use the CPU pane of Activity Monitor to see how apps (processes) are affecting your CPU:

  1. Open Activity Monitor, then choose View > All Processes.
  2. Click the top of the “% CPU” column to sort by the percentage of CPU capability used by each process. 

CPU pane of Activity Monitor

Apps normally use a larger percentage of the CPU when doing tasks that require intensive calculations, such as encoding video. But CPU use should decrease when the task is finished, and it should stop entirely when the app is no longer open. Any process consistently using more than 70 percent of your CPU is putting a significant load on the CPU and could be malfunctioning.

Activity Monitor may show that a process named kernel_task is using a large percentage of your CPU, and during this time you may notice a lot of fan activity. This process helps manage temperature by making the CPU less available to processes that are using the CPU intensely. In other words, kernel_task responds to conditions that cause your CPU to become too hot. When the temperature decreases, kernel_task automatically reduces its activity. 

Quit any malfunctioning processes

To quit a process, first try quitting it normally. For example, quit Safari by switching to Safari and choosing Safari > Quit Safari.

If you can't quit a process normally, you can use Activity Monitor to force it to quit. Save any documents related to the process, then select the process in Activity Monitor and choose View > Quit Process.

If you don't recognize the name of a process, it might belong to OS X or another process that you do recognize. To see the relationships between processes, choose View > All Processes, Hierarchically. If you see that a process belongs to an app, such as Safari or Mail, quit the app before deciding whether to quit any of its processes.

To help avoid malfunctioning processes, keep your apps, plug-ins, and operating system up to date.

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