See how apps affect Mac performance, battery runtime, temperature, and fan activity

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 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 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. 

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 except kernel_task that is consistently using more than 70 percent of your CPU is putting a significant load on the CPU and could be malfunctioning. 

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 macOS 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.

• Check for other conditions that make it harder for your Mac stay cool: learn about the fans in your Mac and the operating temperature of Mac notebooks.
• Learn about the batteries in Mac notebooks and how to maximize battery life and lifespan.
• Learn how Spotlight indexing might make the fans run.
• Learn how third-party add-ons might cause unexpected behavior in Safari.