Glossary

Some of the names and phrases contained in iStat Menus can be found below.

System: Percentage of CPU that is being used by processes that belong to macOS.
User: Percentage of CPU that is being used by apps opened by the user.
Idle: Percentage of CPU that is not being used.
Uptime: How long it has been since the last restart.
Load average: The average number of processes waiting to run, for the past minute, 5 minutes, and 15 minutes. This helps gauge the system’s activity level and whether it’s being overworked. Higher numbers suggest more processes are waiting, indicating potential performance issues if the numbers exceed the number of processor cores available.
Efficiency cores: On Apple Silicon Macs, the efficiency CPU cores use less power.
Performance cores: On Apple Silicon Macs, the performance CPU cores use more power, but can get work done faster.

App: Memory used by applications.
Wired: Memory that cannot be moved from RAM to swap.
Compressed: Memory that may be required in the future, and has been compressed for now.
Free: Memory that is not currently being used.
Memory Pressure: Overall memory use efficiency, determined by the amount of free memory, swap rate, wired memory and file cached memory. Lower is better.

Health: A comparison of the battery’s capacity right now verses the designed capacity. Higher is better.