What is WindowServer on Mac?

WindowServer is the part of macOS that draws everything on your screens: every window, the Dock, the menu bar and every animation, on the built-in display and any you plug in. It's essential, and it's always running.

Key points

WindowServer puts every window on screen for every app, so it's always using some CPU and memory.
Many windows, external or very high-resolution displays, screen recording and video make it work harder.
Leave it running: quitting it logs you out and closes every app.

What WindowServer does

Apps don't draw straight onto the screen. Each one hands its windows to WindowServer, which puts them together into the picture you see, with the Dock, the menu bar, shadows, transparency and animations, as often as the screen refreshes: up to 120 times a second on ProMotion displays. It also passes your clicks and typing to the right window.

In Activity Monitor it appears as WindowServer, run by a special macOS account called _windowserver. That's why searches for "_windowserver" lead here: it's the same thing.

Why is WindowServer using so much CPU?

Because your screens are asking a lot of it. The usual causes are many open windows (especially across several desktops), external displays (particularly several at once, or "scaled" resolutions), screen recording or sharing, video, and busy animations.

In readings of a 14-inch MacBook Pro (M1 Max, 64 GB) on its built-in display, WindowServer used 1.0% CPU at a quiet moment in an earlier reading, and 18.5% CPU with apps open and drawing on October 16, 2026. A few percent is normal; it's worth looking into when it stays above about 30% while nothing on screen is changing.

For what to do about it, see WindowServer using high CPU on Mac: what it means and what helps.

Why is WindowServer using so much memory?

It holds a copy of what's on every screen and every open window, so more windows and more or larger displays need more memory. In the readings above it used 639.9 MB and 758.6 MB, as Activity Monitor counts them. Closing windows you're not using, and unplugging displays you don't need, bring it down.

Is WindowServer keeping my Mac awake?

Usually not. If you check what's keeping your Mac awake (in Terminal, pmset -g assertions), WindowServer is often listed as "UserIsActive": that's macOS noting that you just touched the keyboard or trackpad, and it ends by itself. When a Mac won't sleep, another app is usually the cause. In our reading, it was Google Chrome holding the Mac awake for an open video call ("WebRTC has active PeerConnections").

Why did WindowServer crash?

When WindowServer crashes, the screen goes black for a moment and you're back at the login window, with your apps closed. It's usually set off by a display: an external monitor, a dock or adapter, or a macOS bug with either. Update macOS, update the dock's or adapter's software if it has any, and if it keeps happening with one display connected, try without it.

Can I quit WindowServer?

No. Quitting it logs you out and closes every app, and macOS starts it again at the login window. It settles by itself as soon as there's less on your screens.

How to check it

Open Activity Monitor: press Command-Space, type "Activity Monitor" and press Return.
Type WindowServer in the search field at the top right.
Look at % CPU and Memory. In Activity Monitor, 100% CPU means one full core.

Questions