What Is the Process WindowServer, and Why Is It Running on My Mac?

While checking the Activity Monitor, you noticed something called WindowServer occasionally taking up a bunch of CPU power. Is this process safe?

This article is part of our ongoing series explaining various processes found in Activity Monitor, like kernel_taskhidd, mdsworkerinstalld, and many others. Don’t know what those services are? Better start reading!

WindowServer is a core part of macOS, and a liaison of sorts between your applications and your display. If you see something on your Mac’s display, WindowServer put it there. Every window you open, every website you browse, every game you play—WindowServer “draws” it all on your screen. You can read more at Apple’s developer guide if you’re technically inclined, but it’s not exactly light reading.

For the most part, just know that WindowServer is what macOS, and every application you run on it, uses in order to display things on your screen. It is completely safe.

Why Is WindowServer Using So Much CPU?

As we’ve said, every application communicates with WindowServer in order to draw things on your display. If WindowServer is taking up a lot of CPU power, try closing applications and seeing if the usage drops. If you see a particularly large drop after closing a specific program, that program is probably responsible for the high CPU usage.

To some extent, this is normal: programs that constantly change what’s showing on the screen are going to use WindowServer quite a bit, which means they will use up CPU power. So it makes sense for games, video editors, and other constantly refreshing applications to cause a spike in WindowServer CPU usage.

Having said that, sometimes a bug in a piece of software can cause excessive WindowServer CPU usage. If you notice this pattern, and don’t think the application should be causing that big a spike in WindowServer CPU usage, consider contacting the developer. You might have found a problem they can fix.

If WindowServer keeps using up a lot of power even when you don’t have much of anything running, there are still a few things you can try. First, check our article about speeding up a slow Mac, in particular the section about reducing transparency. You’ll find this option in System Preferences > Accessibility > Display, and it’s been known to reduce WindowSever CPU usage, particularly on older Macs.

You can also try closing unnecessary windows, ensuring there aren’t too many icons on your desktop, and reducing the number of desktops you use in Mission Control. If none of this works, consider resetting the NVRAM; that can help in some cases.

One more thing to keep in mind: if you use multiple monitors, WindowServer is going to use more CPU power in order to draw to multiple displays. The more displays you add, the more true this is.

Photo credit: Hamza Butt

Justin Pot is a staff writer for How-To Geek, and a technology enthusiast who lives in Hillsboro, Oregon. Follow him on Twitter and Facebook, if you want. You don't have to.