What is WindowServer?

WindowServer draws everything you see on your Mac screen.

What does it do?

Every window, every animation, every pixel on your display goes through WindowServer. Its jobs include:

• Layering windows: combining windows from different apps into the final picture on screen
• Tracking windows: keeping track of where each window is, how big it is, and which is in front
• Animations: smooth window shrinking, Mission Control, switching between spaces
• Effects: blur, shadows, and see-through windows
• The cursor: drawing the mouse pointer and changing its shape
• Display output: sending the final picture to all connected screens
• Input routing: sending mouse clicks and key presses to the right window

Why does it use so much processor time?

WindowServer works harder when:

• You have more than one display
• You use a high-resolution (Retina) display, which has four times the pixels of a standard screen
• See-through effects and blur are turned on
• Many windows are open
• Animations are playing
• Video is running alongside other windows

How to reduce its processor use

• Turn down see-through effects: System Settings, then Accessibility, then Display, then Reduce transparency
• Turn down motion: System Settings, then Accessibility, then Display, then Reduce motion
• Close windows you do not need
• Unplug extra screens you are not using
• Lower the display resolution

Can you restart it?

Restarting WindowServer logs you out, because it manages all windows. If it crashes, macOS restarts it on its own and returns you to the login screen. Do not kill it yourself.

Should you worry?

No. It is the most important display process on macOS. If it uses a lot of processor time, it is working hard to draw a busy desktop. Reduce visual effects if it becomes a problem.

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