Activity Monitor on Mac — How to Monitor System Resources on macOS

Activity Monitor ships with every version of macOS and requires no additional installation. Apple organizes the utility into five tabs — CPU, Memory, Energy, Disk, and Network — each presenting a different category of system metrics. The process list in each tab shows every active task, including background daemons and kernel processes, sorted by resource consumption.

MoniThor builds on the same underlying system data that Activity Monitor reads, presenting it in the macOS menu bar where it remains visible at all times. For a complete overview of what MoniThor displays, visit the Features page.

The fastest method is Spotlight: press Cmd+Spaceto open the search bar, type "Activity Monitor," and press Return. macOS indexes the application name, so typing the first few characters is usually sufficient.

Alternatively, open Finder, click Go > Utilities in the menu bar, or press Cmd+Shift+U to open the Utilities folder directly. Activity Monitor is listed alphabetically among the other system utilities.

For frequent access, drag Activity Monitor to the Dock or set it as a Login Item in System Settings > General > Login Items so it launches automatically at startup.

The %CPU column indicates the percentage of total CPU time each process consumes. A value above 100% is normal on multi-core Macs because each core contributes up to 100%. The bottom bar separates usage into "User" (application code) and "System" (kernel and driver operations).

Sorting the list by %CPU helps identify runaway processes that drain battery life or cause fan noise. Double-clicking a process opens a detail inspector with threads, open files, and memory maps. The Mac CPU usage guide covers CPU monitoring in greater detail.

The memory pressure graph is the most important indicator. Green means the system has ample free memory. Yellow indicates the system is compressing memory to make space. Red signals heavy swap usage, which degrades performance because disk I/O is orders of magnitude slower than RAM.

Wired memory is reserved by the kernel and cannot be paged out. Compressed memory has been algorithmically shrunk to fit more data into physical RAM. Cached files memory holds recently accessed file data for faster re-reads. The RAM usage guide explains these categories and how to interpret them.

Activity Monitor occupies a full application window that competes with other windows for screen space. Checking a single metric — such as current CPU load — requires switching away from the active application, locating the Activity Monitor window, and switching back.

The utility does not support persistent monitoring. Closing the window means losing visibility into system state until you reopen it. There is no option to pin a small summary to the menu bar or display live sparkline graphs that show trends over time.

Activity Monitor also lacks configurable keyboard shortcuts. There is no way to invoke a quick summary overlay without first bringing the full window to the foreground.

MoniThor reads the same underlying system data as Activity Monitor but presents it persistently in the menu bar. CPU load, memory pressure, network throughput, and disk activity are visible at a glance without switching applications or managing extra windows.

Sparkline graphs in the menu bar show the last 60 samples of each metric, making it easy to spot trends — a sudden CPU spike, a memory pressure climb, or a network throughput drop — without opening a dashboard. Configurable keyboard shortcuts let you invoke the expanded dashboard instantly from any application.

For a full breakdown of every metric MoniThor monitors, visit the Features page. To learn how MoniThor compares to other monitoring tools, return to the home page.