What is SystemUIServer on Mac?

SystemUIServer runs some of the icons in your Mac's menu bar, the strip at the top of the screen. It's part of macOS and safe.

Key points

• SystemUIServer runs some of the menu bar's icons.
• It's rarely busy.
• Quitting it doesn't help for long: macOS starts it again, which also makes it a quick fix for a stuck menu bar.

What SystemUIServer does

Some of the icons on the right of the menu bar are drawn by SystemUIServer rather than by an app. Control Center has its own process in recent versions of macOS, so SystemUIServer does less than it used to.

Why is SystemUIServer using CPU?

It's rarely busy. If it is, an icon in the menu bar is usually stuck.

In one reading of a MacBook Pro (M1 Max, 64 GB) on October 10, 2026, SystemUIServer was using 0.0% of the CPU and 11.6 MB of memory.

How to restart SystemUIServer

If menu bar icons stop responding:

1. Open Terminal.
2. Type killall SystemUIServer and press Return.
3. The menu bar icons disappear for a second and come back.

Can I quit SystemUIServer?

Stopping it doesn't help for long: macOS starts it again when it's needed. That's what makes restarting it safe.

How to check it

1. Open Activity Monitor: press Command-Space, type "Activity Monitor" and press Return.
2. Type SystemUIServer in the search field at the top right.
3. Look at % CPU and Memory.

Questions

Is SystemUIServer a virus?

No. SystemUIServer is part of macOS: it runs some of the menu bar's icons.

How do I restart SystemUIServer?

In Terminal, type killall SystemUIServer and press Return. macOS starts it again within a second.

Why is SystemUIServer not responding?

Usually a menu bar icon is stuck. Restarting it reloads the icons.