# WindowServer high CPU on Mac: why it happens and how to lower it > WindowServer draws everything on your screen. Extra displays, transparency, many windows and busy apps push its CPU up. How to lower it on macOS 26. Updated: 2026-10-12 · Tested on: MacBook Pro 14" (M1 Pro, 16 GB) + external 1080p display at 170 Hz, macOS 26.3 Tahoe · Applies to: macOS 13 Ventura – 26 Tahoe · Author: Tu Nguyen, OneClickTool Studio ## Short answer - WindowServer is the macOS process that draws every window, menu and animation on your displays, so its CPU use rises with how much is on screen. - The biggest causes are extra or high-refresh displays, scaled resolutions, transparency effects, many open windows and apps that animate constantly. - Turn on Reduce transparency in System Settings › Accessibility › Display, close windows you are not using, and quit apps that redraw all the time. - Logging out and back in restarts WindowServer and clears a stuck state; force quitting it from Activity Monitor logs you out without saving. ## What WindowServer does Every app draws its own windows, but something has to put them all together into the image on your screen: stacking windows, drawing shadows and blur, moving the pointer, playing animations, and sending the result to every display. On a Mac that process is **WindowServer**. Because of that, WindowServer's CPU use is a measure of how much drawing your screen needs. It goes up when: - there are more pixels to draw (more displays, higher resolutions), - they change more often (high refresh rates, video, animated web pages), - each frame is more expensive (transparency, blur, many overlapping windows). ## Check how busy it is Open **Activity Monitor**, click the **CPU** tab and find WindowServer. Or run this in Terminal, which only reads: ``` top -o cpu -n 5 -l 2 -stats pid,command,cpu | tail -6 ``` On our test Mac, a 14-inch MacBook Pro with its built-in display plus an external 1080p display at 170 Hz, WindowServer measured **29.9% to 31.5%** CPU across two samples with ordinary apps open. That is our baseline, not a problem in itself. It becomes one when the pointer stutters, windows lag when you drag them, or the fans run with nothing heavy open. ## 7 ways to lower WindowServer CPU ### 1. Turn on Reduce transparency Go to **System Settings › Accessibility › Display** and turn on **Reduce transparency**. Menus, the Dock and sidebars become solid instead of blurred, which is less work to draw. On macOS 26 Tahoe, whose Liquid Glass design uses more transparency, this is the first thing to try. ### 2. Turn on Reduce motion In the same pane, **Reduce motion** replaces sliding and zooming animations with simple fades. Apple describes it in [Customize onscreen motion on Mac](https://support.apple.com/guide/mac-help/customize-onscreen-motion-mchlc03f57a1/mac). ### 3. Lower the refresh rate of external displays A 144 Hz or 170 Hz display asks WindowServer to redraw that many times a second. In **System Settings › Displays**, select the external display and set **Refresh rate** to 60 Hz when you do not need the smoothness, for example while writing or in meetings. ### 4. Use the default resolution Scaled resolutions ("More space" or a custom size that does not match the panel) make the Mac draw a larger image and then shrink it. In **System Settings › Displays**, choose the option marked **Default** for each display and compare. ### 5. Close windows and tabs you are not using Every open window is a layer WindowServer has to keep track of, even behind others. Minimised windows and windows on other desktops count too. Quit apps you are done with rather than leaving them open with windows. ### 6. Find the app that keeps redrawing Some apps animate all the time: a browser tab with video ads, a chat app with animated emoji, a menu bar app that updates every second. Quit apps one at a time while watching WindowServer in Activity Monitor; when it drops, you found the cause. Screen recording and screen sharing also add load while they run. ### 7. Log out and back in If WindowServer stays high after you closed everything, log out from the **Apple menu** and log back in. That restarts WindowServer cleanly. Force quitting WindowServer in Activity Monitor has the same effect but closes every app without saving, so use it only when the Mac is frozen. > **Don't** delete WindowServer preference files or run scripts that promise to "reset" it. They can reset your display arrangement and color profiles, and they rarely fix the CPU use. ## When it is not WindowServer If **kernel_task** is the process at the top instead, the Mac is cooling itself down; see [kernel_task using high CPU](https://oneclicktool.app/fix/slow-mac/kernel-task-high-cpu). A nearly full startup disk also slows everything down, because macOS needs free space for swap files; our [storage checklist](https://oneclicktool.app/fix/storage/mac-storage-full) helps there. More slow-Mac causes are collected on the [slow Mac page](https://oneclicktool.app/fix/slow-mac). ## FAQ **What is WindowServer on Mac?** It is the part of macOS that combines the windows of every app into the picture you see on each display. It always runs; when it uses a lot of CPU, the screen and animations can stutter. **Is 30% CPU for WindowServer normal?** With several displays or a high refresh rate it can be. On our test MacBook Pro with one extra 1080p display at 170 Hz, WindowServer sat at about 30% while apps were open. Steady use far above that, with lag, is worth fixing. **Can I quit WindowServer?** You can force quit it in Activity Monitor, but that ends your session immediately and closes apps without saving. Logging out from the Apple menu does the same safely. **Does macOS Tahoe use more WindowServer CPU?** Tahoe's Liquid Glass design uses more transparency and blur. Turning on Reduce transparency lowers that drawing work. We have not measured a before-and-after number ourselves. ## Sources - [Activity Monitor User Guide for Mac — Apple Support](https://support.apple.com/guide/activity-monitor/welcome/mac) - [Customize onscreen motion on Mac — Apple Support](https://support.apple.com/guide/mac-help/customize-onscreen-motion-mchlc03f57a1/mac) Source: https://oneclicktool.app/fix/slow-mac/windowserver-high-cpu