macOS processes › Display and graphics
What is WindowServer on Mac?
WindowServer is the macOS process that draws everything you see. It combines every app's windows, the menu bar and the Dock into the image on each display, and it gets busier with more displays, more open windows and more animation.
What it does
Apps don't draw straight to the screen. They hand their window contents to WindowServer, which layers them with transparency and shadows, applies effects, and sends the result to every connected display. It also routes mouse and keyboard events to the right window. Its CPU and GPU use rise and fall with how much on screen is changing.
Why it gets busy
- More or larger displays, especially external displays set to a scaled resolution, which means drawing more pixels.
- Lots of open windows or Spaces, or an app that redraws constantly, like an animated web page or a menu bar app updating many times a second.
- Transparency and motion effects, and dynamic or Aerial wallpapers.
- Screen recording, screen sharing and video calls, which read the screen continuously.
- Early in macOS Tahoe's release, outdated Electron-based apps were reported to make WindowServer busy. Updating those apps fixed it.
Why is WindowServer using so much CPU?
WindowServer uses CPU when something on screen keeps changing: many windows, several displays, animation, transparency or screen recording. Find the app that redraws constantly and cut back visual effects, and it drops.
Is it safe to quit?
Force quitting WindowServer logs you out immediately and closes every app without saving.
The real WindowServer runs from inside /System/Library/PrivateFrameworks/SkyLight.framework.
How to calm it down
- Close windows and tabs you aren't using, and quit apps sitting in other Spaces.
- Turn on Reduce transparency and Reduce motion in System Settings › Accessibility › Display.
- Pick a still wallpaper instead of a dynamic or Aerial one in System Settings › Wallpaper.
- For an external display, try its default resolution in System Settings › Displays instead of a scaled one.
- Update your apps, especially Electron-based ones like chat apps and code editors.
In SystemWatch
SystemWatch's History shows whether WindowServer spikes start when you connect a display or open a particular app, which points to the real cause.
