Stop macOS System UI Server high CPU after sleep

The quick fix (30 seconds) — relaunch System UI Server

This is the first thing you try. It works about 8 out of 10 times on recent macOS versions (Ventura 13.4+, Sonoma 14.x). The bug seems to be a graphics state that gets stuck when the Mac wakes from sleep — especially on MacBooks with M1 or M2 chips, but I've also seen it on Intel Macs running Monterey.

Open Terminal (found in Applications > Utilities). Don't be scared of commands — this one is harmless. Type exactly this and hit Return:

sudo killall SystemUIServer

You'll need to type your password. It won't show any characters as you type — that's normal. After you press Return, the menu bar will flicker for a split second. The System UI Server process restarts cleanly.

After this step: Open Activity Monitor (Applications > Utilities). Click the CPU tab. If System UI Server is gone from the list, or using under 10% CPU, you're done. If it's back and still high, move to the next fix.

The moderate fix (5 minutes) — clear caches and preferences

If the killall command didn't stick, there's likely a corrupted cache file or preference file that's causing the process to loop. This happens more often after a macOS update that didn't clean up old data.

First, quit any open apps and save your work. Then open Finder. From the menu bar at the top, click Go > Go to Folder (or press Shift+Command+G). Type this path and click Go:

~/Library/Caches

This is your user folder's cache directory. Look for any folder that starts with com.apple.systemuiserver. If you see one, drag it to the Trash. You might also see a file called com.apple.systemuiserver.plist — delete that too.

Next, go to Go > Go to Folder again and type:

~/Library/Preferences

Find any file named com.apple.systemuiserver.plist — there's usually just one. Delete it. Empty the Trash.

Now reboot your Mac. After rebooting: check Activity Monitor again. If CPU usage is normal (under 5% when idle), you're set. If it's still high, the problem is deeper — probably a system extension or third-party utility conflicting with the display server.

Check for conflicting software

Common culprits: Bartender, Magnet, Rectangle, BetterTouchTool, or any app that modifies the menu bar or window management. Also look at apps that add icons to the menu bar — Dropbox, Google Drive, or backup software. Quit them one by one in Activity Monitor and see if CPU drops. If you find the troublemaker, update it or remove it.

The advanced fix (15+ minutes) — reset NVRAM, SMC, and check disk

If the first two fixes didn't work, something's broken at the firmware or disk level. This is rare but happens — especially after a failed macOS update or a power loss during sleep.

Reset NVRAM (non-volatile RAM)

This works on Intel Macs. On Apple Silicon (M1/M2/M3), NVRAM resets automatically during startup — you don't need to do this manually. If you're on Intel:

1. Shut down your Mac completely.
2. Turn it on and immediately press and hold these four keys together: Option + Command + P + R.
3. Hold for about 20 seconds. You'll hear the startup chime twice (or see the Apple logo appear and disappear twice).
4. Release the keys. Let the Mac boot normally.

After this step: The menu bar might look slightly different (your custom menu bar settings could reset). That's normal. Check CPU usage in Activity Monitor. If it's down, you're good.

Reset SMC (System Management Controller)

Also Intel-only. Apple Silicon Macs don't have a separate SMC — it's built into the SoC. For Intel laptops with a non-removable battery (most 2016 and later):

1. Shut down the Mac.
2. Press and hold the Control + Option + Shift keys on the left side of the keyboard, plus the power button.
3. Hold all four keys for 10 seconds. The Mac might turn on briefly — that's fine.
4. Release all keys. Press the power button normally to start.

After this step: Your fan might spin up once during boot — that's the SMC recalibrating. Check CPU again. If System UI Server is still high, run Disk Utility.

Run First Aid on your startup disk

Sometimes the issue is a corrupted file system that macOS can't read properly, causing the display server to hang. Open Disk Utility (Applications > Utilities). Select your startup disk (usually called "Macintosh HD"). Click First Aid, then Run. Let it complete — it could take 10–15 minutes on an older Mac. It won't erase your data.

After First Aid finishes: It'll say "Operation successful" or list errors it fixed. Reboot. Check CPU one more time. If you still see high usage, the problem might be hardware — a failing GPU on Intel Macs or a logic board issue on Apple Silicon. In that case, you're looking at a trip to the Apple Store or an authorized repair shop.

Why this happens (the short version)

The System UI Server handles your menu bar, dock, and window compositing. When a Mac wakes from sleep, it runs a checksum on all its cached state data. If that data is corrupt or too old, the process can get stuck in a loop trying to reconcile mismatched info. That's why deleting caches fixes it — you're giving the process a clean slate to rebuild from.

The killall command works as a band-aid because it forces the process to reload. But if the corrupt file is still there, it'll crash again on the next wake cycle. That's why you need to delete the specific files.