Threads

In Activity Monitor, click the CPU tab. The Threads column shows the count per process, and the bottom of the window shows the total number of threads and processes on the Mac.

In Terminal, ps -M -p <PID> lists the threads of a single process.

A thread count that keeps climbing over hours, without leveling off, can point to a bug where an app starts threads and never ends them. If that app also grows in memory or slows down, restarting it is a reasonable first step, and reporting it to the developer helps.

macOS gives apps a shared pool of worker threads through Grand Central Dispatch. When an app hands off many small tasks, such as decoding images or reading files, the pool can grow to handle them and shrink again later. That alone can add dozens of threads to a busy app.

Browsers, chat apps and code editors often run several processes, each with its own threads for drawing, networking, audio and scripts. Audio and video apps keep threads ready so playback never has to wait. Add these up and a few hundred threads in one large app is not unusual.

kernel_task often shows the largest count of all. It holds the threads the macOS kernel and its drivers use, and it is not a sign of a problem.

1. In Activity Monitor, select the process and double-click it, or click the Info button in the toolbar.
2. The inspector window lists Threads along with Ports and Context Switches for that process.
3. In Terminal, run top -l 1 -pid <PID> -stats pid,command,th, replacing <PID> with the process ID from the PID column. The #TH value shows total threads, then running threads after the slash.
4. To sort every process by thread count, run top -o th -stats pid,command,th and press q to exit.

The total matters less than the direction it moves over time.

• Normal: the count jumps when you open windows, start a download or begin an export, then falls back when the work is done.
• Normal: a steady, high count that stays about the same for hours.
• Worrying: a count that climbs all day and never falls, even while the app is idle.
• Worrying: a climbing thread count together with growing memory or a growing Ports count. That combination usually points to a leak in the app.
• Worrying: many running threads, shown after the slash in top, in an app you are not using. It is doing work you did not ask for.

Having more threads than cores is normal. macOS switches cores between threads many times a second, and most threads are waiting anyway. Only running threads compete for a core.

The number of threads that can run at the same moment equals your logical core count from sysctl -n hw.logicalcpu. If more threads are ready than that, the extra ones wait, and that waiting is what raises the load average.