Memory column

Many apps run helper processes, and each helper has its own row. A browser can show a modest figure on its main row while its helpers add up to much more. Use View, All Processes, Hierarchically to see some helpers under their parent, or add the rows yourself.

Sort by it when memory pressure is yellow or red. Watch whether a process keeps growing over time while you are not doing more with it, which can point to a leak. Quitting and reopening the app releases its memory.

You can add other memory columns from View, Columns, such as compressed memory, to see more detail per process.

macOS keeps a running count for every process called its physical footprint. It tracks the memory the process has written to and owns. The Memory column in Activity Monitor and the MEM column in the top command both show this count.

Because it counts memory the process owns rather than only what is sitting in RAM right now, it can include compressed data and memory used for graphics on behalf of the process. It leaves out files the process has only read, which the system can drop and read again later.

Some memory a driver or system component sets aside on behalf of a process is deliberately left out of its footprint, because the process has no control over its size. So the Memory column is a good guide for comparing processes, but not an exact record of every byte a process caused the system to use.

In the Memory tab, choose View > Columns to add more memory columns. Each one counts something different:

• Memory: the process's physical footprint. Use this one to compare processes.
• Real Mem: how much of the process is in RAM right now, also called resident size. It leaves out compressed data and can include shared memory, so it can be higher or lower than Memory.
• Private Mem: resident memory used only by this process.
• Shared Mem: resident memory the process shares with other processes, such as system libraries.
• Purgeable Mem: memory the app has marked as safe for the system to discard if it needs room.
• VM Compressed: how much of the process's memory has been compressed.

These commands only read information. They are useful when Activity Monitor is not open or you want to log a number over time.

1. Run top -o mem to list processes sorted by memory. The MEM column matches Activity Monitor's Memory column. Press q to quit.
2. Run top -l 1 -o mem -n 10 -stats pid,command,mem to print the ten largest processes once and exit.
3. Run footprint followed by an app name, such as footprint Safari, to see its memory by category. The phys_footprint line at the end matches the Memory column, and phys_footprint_peak is the highest it has been since the process started.
4. Be aware that ps shows RSS, which is resident size like the Real Mem column, so its numbers will not match the Memory column.

1. In the Memory tab, choose View > Update Frequency > Very often (1 sec) if you want faster updates.
2. Find the app, including its helper processes, and note its Memory figure.
3. Keep using the app the way you normally do, without opening more documents or windows.
4. Check the figure again after some time. If it keeps climbing and never drops back, even when you close what you opened, the app is likely leaking memory.
5. Quit and reopen the app to release the memory. If it happens again, check for an update to the app.