App Memory

Sort the Memory tab by the Memory column. Remember that apps with many helper processes, like browsers, are spread across several rows, so add those together to see the app's real total.

A large App Memory figure is not a problem on its own. Check memory pressure: if it is green, the Mac is coping. If App Memory keeps climbing for one app over hours without you doing more in it, that app may have a memory leak, and quitting and reopening it will release the memory.

At the bottom of Activity Monitor's Memory tab, Memory Used is broken into three parts: App Memory, Wired Memory and Compressed. Physical Memory is the total RAM installed, and Cached Files is listed separately because apps can take it back when they need it.

Activity Monitor describes App Memory as physical memory allocated by apps and system processes. So it is not only the apps in your Dock. Background services that macOS runs for you count here too.

App Memory rises when you open apps and documents and falls when you quit them. That is the part of Memory Used you can change directly.

1. Open Activity Monitor and click the Memory tab.
2. Choose View > All Processes, Hierarchically. Many helper processes are shown under the process that started them, which makes it easier to see which app they belong to.
3. Click the Memory column heading to sort by it.
4. Double-click a process, or select it and click the Info button, to open its details. The Memory tab of that window shows figures such as Real Memory Size, Private Memory Size and Shared Memory Size.
5. Quit apps you are not using and watch App Memory and Memory Pressure at the bottom of the window.
6. Leave system processes you do not recognize alone. Many of them restart right away when quit, and some are needed for the Mac to work, so quitting them does not lower App Memory for long.

macOS includes a command called footprint that shows how an app's memory is used. It only reads information and does not change anything. For example, run footprint Safari to see Safari's main process.

The output lists memory by category and ends with a total. Under Auxiliary data, phys_footprint is the current figure, the same kind of number Activity Monitor shows in its Memory column, and phys_footprint_peak is the highest it has been since the app opened. A peak far above the current value means the app needed a lot of memory at some point and has since given much of it back.

You can check processes you own without extra steps. To inspect processes that belong to the system or another user, footprint needs to run as root.

A high App Memory figure is normal while memory pressure is green. It becomes a problem when App Memory keeps rising while you are not opening anything new, and memory pressure turns yellow or red. The usual reasons are:

• Browsers, where every tab and extension can run in its own process.
• Chat, email and other apps built on web technology, which also run several helper processes.
• Photo, video, audio and 3D apps holding large files in memory.
• Virtual machines and developer tools.
• An app that has been open for days and keeps growing.