% GPU

Open Activity Monitor and click the CPU tab. If you do not see % GPU, choose View > Columns and check it. Click the column header to sort.

The View menu also has a GPU Processes option that limits the list to processes using the GPU.

Apple suggests checking GPU activity if your Mac feels hot or the battery drains quickly. Sustained GPU work produces heat and uses energy, just like CPU work.

An empty desktop does not mean an idle GPU. Sort the % GPU column and you will usually find one of these:

• WindowServer drawing the screen. It does more work with more displays, higher resolutions and more motion on screen.
• A browser tab in the background that plays video, runs animations or draws with WebGL.
• A video call app that is still open, especially with background effects on.
• An app hidden behind other windows that keeps redrawing, such as a game at its menu screen.
• Apps that run machine learning or image work in the background on the GPU.

% GPU is what the process is using right now. GPU Time is the total GPU time the process has used since it started, the same idea as the CPU Time column. A process with low % GPU but a GPU Time that keeps growing is using the graphics chip in the background.

The View menu has two GPU filters. GPU Processes shows only the processes using the GPU. Processes, by GPU groups them under each GPU, which helps on Macs with more than one graphics processor.

On a Mac with Apple silicon, the GPU is part of the same chip as the CPU and shares its unified memory. There is one GPU, and its use shows up in the same heat and battery figures as the CPU.

Some Intel Macs have two graphics processors: an integrated one that uses less power and a separate, faster one. The Energy tab shows whether an app requires the high performance GPU, since that one uses more energy.

Apple's GPU History help suggests an external GPU if the graph is full of tall bars. External GPUs only work with Intel Macs, not with Apple silicon.

sudo powermetrics --samplers gpu_power -n 1 takes one sample and prints GPU frequency, how much of the time the GPU was active, and an estimate of GPU power. It asks for your administrator password and only reads data.

On Apple silicon, ioreg -r -d 1 -w 0 -c IOAccelerator | grep -o '"Device Utilization %"=[0-9]*' prints the current use of the whole GPU as a single percentage, with no password needed.