You installed macOS 27, and now the fans spin up during a video call, the battery drops faster than it did last week, and apps take a beat longer to open. It's easy to assume the update broke something.

Usually it didn't. A major macOS upgrade leaves your Mac with hours of background work, and Golden Gate has more of it than most releases. Here's how to confirm that's what you're seeing, how to help it finish, and when to stop waiting.

Why the first days are slower

After a major upgrade, several system services rebuild their data at the same time:

  • Spotlight re-indexes your drive. Every file, email, message, and document gets catalogued again. Golden Gate uses a reworked indexing system, so this is closer to a full rebuild than a quick refresh.
  • Photos re-analyzes your library for faces, objects, scenes, and text in images.
  • Mail rebuilds its message index so search works across your mailboxes.
  • iCloud re-syncs Drive, Photos, and other data to check that local copies match.
  • Apple Intelligence downloads its models and runs setup tasks after the upgrade finishes.

All of that competes for CPU, storage I/O, and battery. How long it takes depends on how much data you have. A lightly used MacBook Air might settle in a day. A Mac with a 200 GB Photos library and years of mail can take three days or more.

Confirm it's indexing, in 60 seconds

Open Activity Monitor (Applications > Utilities), click the CPU tab, and sort by the % CPU column.

If the top of the list includes processes like these, your Mac is doing post-upgrade housekeeping:

Process What it's doing
mds, mds_stores, mdworker_shared Spotlight indexing
photoanalysisd, mediaanalysisd Photos library analysis
cloudd, bird iCloud sync
Processes with intelligence in the name Apple Intelligence setup

Prefer Terminal? This shows the 15 busiest processes:

ps -Ao %cpu,comm -r | head -15

Check that Spotlight indexing is enabled on your startup volume:

mdutil -s /

If it reports that indexing is enabled and the md processes are busy, you're looking at a rebuild in progress.

Help it finish faster

The fastest way through this is to let the Mac work while you're not using it.

  1. Plug it in overnight. macOS defers some heavy background tasks until the Mac is on power.
  2. Keep it awake with the lid open or on a display. In System Settings > Battery > Options, turn on the setting that prevents automatic sleeping on power adapter when the display is off. Turn it back off once things settle.
  3. Stay on a stable network. iCloud sync and model downloads stall on flaky Wi-Fi.
  4. Don't force-quit indexing processes. macOS restarts them, and the work starts over, stretching the slow period instead of ending it.
  5. Skip Low Power Mode while plugged in overnight. It helps battery life during the day, but it also slows background work down. Use it when you're on battery and need the hours; turn it off when you want indexing to finish.

What else to check while you wait

Not every slowdown after an upgrade is indexing. These are the common culprits that look similar.

Login items that came back. Major upgrades can re-enable background helpers you turned off. Open System Settings > General > Login Items & Extensions and review both "Open at Login" and the "Allow in the Background" list. Turn off anything you don't recognize or don't need.

Apps that haven't been updated for 27. An app that's incompatible often spins in the background instead of crashing outright. In Activity Monitor, switch to the Energy tab and sort by 12 hr Power. An app you barely used today sitting near the top is a red flag. Update it, or quit it and see whether things improve.

Something preventing sleep. If the battery drains overnight with the lid closed, check what's holding the Mac awake: 

pmset -g assertions

Look for PreventUserIdleSystemSleep entries and the process that owns them. Backup tools, sync clients, and browsers with media tabs are frequent offenders.

Utilities that hook into the system. Window managers, mouse and keyboard remappers, and menu bar tools can misbehave on a new release. Some users have reported Mission Control actions failing through third-party mouse utilities on Golden Gate. Check for updates to each one, or quit them temporarily to rule them out.

WindowServer running hot. If WindowServer sits high on the CPU list, the cost is in drawing the interface. This is more noticeable with many open windows, external displays at scaled resolutions, or on older Apple silicon. Try lowering Liquid Glass transparency with the new control, or turn on Reduce Transparency in System Settings > Accessibility > Display, and see whether it drops.

When it's not normal anymore

Give it three to four days of normal use, with at least one night plugged in. After that, these are signs of a real problem rather than housekeeping:

  • The md or photoanalysis processes are still near the top of the CPU list every day.
  • A single non-system process sits at high CPU for hours regardless of what you're doing.
  • The Mac is hot and the fans run while idle, with nothing obvious in Activity Monitor.
  • kernel_task is using a lot of CPU. That's macOS managing heat, which means something else is generating it.
  • Battery life is still dramatically worse than before, and the Energy tab doesn't point to any one app.

What to do if it's still slow

Work through these in order. Each rules out a layer.

1. Update everything again. Apps and macOS itself. Apple often ships a small 27.0.x update in the first weeks, and developers push compatibility fixes after release.

2. Boot into Safe Mode. Safe Mode loads only essential software and clears some system caches. On Apple silicon: shut down, press and hold the power button until startup options appear, select your startup disk, then hold Shift and click Continue in Safe Mode. If the Mac is fine in Safe Mode, a third-party login item or extension is the likely cause.

3. Test with a fresh user account. Create a new user in System Settings > Users & Groups and log in. If the new account is fast, the problem lives in your user settings or apps, not in the system.

4. Rebuild the Spotlight index, only if indexing is stuck. If Spotlight has been at it for a week with no end in sight: 

sudo mdutil -E /

This erases and rebuilds the index, which means another round of indexing. Do it once, plug in overnight, and don't repeat it.

5. Report it. Use the Feedback Assistant app to send Apple a report, with a sysdiagnose if you can. Specific, reproducible reports are what get fixed in the next update.

What not to do

  • Don't reinstall macOS on day one. It restarts all the background work you're waiting on.
  • Don't turn off Spotlight permanently to save battery. Mail search, Siri AI, and app search depend on it.
  • Don't run "memory cleaner" apps. Purging memory forces macOS to reload what it just cached, which costs more energy than it saves.
  • Don't roll back to Tahoe out of impatience. It means erasing your Mac and restoring from a pre-upgrade backup, and the slowdown you're escaping is probably a few days from ending on its own.

The short version

For the first two to three days, heavy CPU from mds, photoanalysisd, and iCloud processes is normal. Plug in overnight, don't kill anything, and check Login Items and outdated apps in the meantime.

If it's still happening after four days, go through Safe Mode, a test user account, and a one-time index rebuild. By then you've either found the culprit or collected exactly the details Apple needs to fix it.