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Mac slow after a macOS update? Why it happens and how to fix it

Updated · 2 min read · by

Quick answer

After a macOS update, your Mac rebuilds its Spotlight index, re-analyses photos and refreshes caches in the background. That can make it feel slow, warm or loud for several hours to a day. Leave it plugged in and awake for a while. If it's still slow after a couple of days, update your apps, review login items and check free disk space.

Why a Mac feels slow right after an update

A macOS update changes a lot of the system at once, and several services catch up afterwards:

This is temporary. It usually settles within a day, faster if your Mac stays on power.

How to speed things up

  1. Leave your Mac plugged in and awake for a few hours, ideally overnight with the lid open on a MacBook. Background work runs best when you're not using it.
  2. Check what's busy. Open Activity Monitor, click the CPU tab and sort by % CPU. If the top items are indexing and analysis processes, give them time.
  3. Update your apps. Older versions of some apps run poorly on a new macOS. Check the App Store and each app's own updater.
  4. Review login items. In System Settings › General › Login Items, turn off apps and background items you don't need at startup.
  5. Check free space. In System Settings › General › Storage, keep at least 10 to 15% of the disk free so macOS has room for swap and caches.
  6. Restart once after the first day. It clears anything that got stuck during the update.

If it's still slow after a few days

  1. Look at Memory pressure in Activity Monitor's Memory tab. Yellow or red means you need fewer apps open, or more memory.
  2. Try Safe Mode to rule out a startup item or extension. On a Mac with Apple silicon, shut down, press and hold the power button until startup options appear, select your disk, then hold Shift and click Continue in Safe Mode. If the Mac is fast in Safe Mode, a login item or extension is the likely cause.
  3. Check for a stuck process that stays at the top of the CPU list for hours. Our process glossary explains the common ones.
  4. Contact Apple Support if nothing helps, especially if the Mac also crashes or restarts on its own.

Questions people ask

How long is a Mac slow after an update?

Usually from a few hours to a day, while Spotlight and Photos catch up. Large libraries and full drives take longer.

Why are my fans loud after a macOS update?

Background indexing and analysis keep the chip busy for a while. It's normal and stops on its own once they finish.

Should I reinstall macOS if it's slow after an update?

Rarely. Give it a day plugged in, update your apps and review login items first. Reinstalling is a last resort.

Can I stop Spotlight indexing after an update?

You can exclude folders you never search in Spotlight's privacy list in System Settings, but letting the first index finish is the fastest way back to normal.