WindowServer is the part of macOS that draws every window and frame on your displays; it's a normal system process, not malware. Its CPU use rises with more or higher-resolution displays, transparency and lots of open windows, so close windows or turn on Reduce transparency if it stays high.
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One Mac, macOS 26.5 (25F71) on Apple silicon, read with ps and codesign on October 29, 2026
| Path | /System/Library/PrivateFrameworks/SkyLight.framework/Resources/WindowServer |
|---|---|
| Runs as | _windowserver, a macOS system account |
| Signed by | Apple (Software Signing), identifier com.apple.WindowServer |
WindowServer is the core macOS process responsible for compositing and rendering everything you see on screen. It manages all window drawing, animations, transparency effects, display output, and GPU interaction. Its man page describes it as the system daemon for window management, content compositing and event routing.
High CPU usage when driving multiple or high-resolution external displays
Screen tearing, flickering, or rendering glitches
Excessive memory consumption with many windows and spaces open
GPU-related crashes causing a forced logout to the login screen
Go to System Settings > Accessibility > Display and enable 'Reduce transparency' and 'Reduce motion.' These settings significantly lower the compositing workload on WindowServer.
Each open window, Space, and desktop adds compositing overhead. Close windows you're not actively using, reduce the number of Spaces in Mission Control, and avoid keeping dozens of browser tabs visible.
Non-native display scaling forces WindowServer to render at a higher resolution and then downscale. Go to System Settings > Displays and choose 'Default' resolution or the native resolution for best performance.
Unlike most processes, WindowServer cannot be restarted without logging out. Save your work, log out from the Apple menu, and log back in to reset WindowServer's state and free any leaked GPU memory.
WindowServer using 20-40% CPU during window animations or when connected to high-res displays is normal. Be concerned if it consistently uses more than 60% CPU while the screen is relatively static, or if it causes repeated forced logouts — these can indicate GPU driver issues or hardware problems.
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WindowServer handles all screen rendering on macOS. High CPU usage typically comes from driving high-resolution displays (especially multiple 4K/5K monitors), heavy animation effects, transparency compositing across many windows, or applications that rapidly redraw their content. Non-native display scaling also significantly increases its workload.
Yes, but it requires logging out. WindowServer is tied to your login session — you cannot kill it from Activity Monitor without being forced to the login screen. The fastest way to restart it is to log out and back in from the Apple menu, which preserves your boot state while resetting WindowServer.
Yes. WindowServer is a core Apple system process that has been part of macOS since its earliest versions, and without it your Mac would have no graphical display at all. On macOS 26.5 it runs as the _windowserver system account from /System/Library/PrivateFrameworks/SkyLight.framework/Resources/WindowServer, is signed by Apple, and sits in a folder System Integrity Protection guards.
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