Mac slow after update: why the first 48 hours are slow and how to tell it is settling

Why a Mac is slow right after an update

A macOS update replaces the system, and several databases that depend on it are rebuilt from scratch afterwards. The Mac is not broken; it is doing a few days of catch-up work in the first day or two, and it does that work while you are trying to use it.

The jobs that restart, and the process names you will see in Activity Monitor:

• Spotlight re-indexing. mds_stores and corespotlightd read every file on the disk to rebuild the search index. On a Mac with hundreds of thousands of files this is the biggest single job. Normally it settles in 10 to 30 minutes after a small change, but a full rebuild after a major update can run for hours.
• Photos analysis. photoanalysisd and mediaanalysisd go back through the Photos library for faces, scenes, text in images and Memories. A big library means an hour or more of work, and it only runs when the Mac is idle and, by preference, plugged in.
• iCloud re-sync. bird (iCloud Drive) and cloudd compare every synced file against the server. Usually minutes, up to a few hours with a large iCloud Drive.
• Security scanning. XProtect runs a fresh malware scan after an update. A pass typically takes 10 to 15 minutes.
• App relaunch and caches. Every app you open for the first time after the update rebuilds its own caches, and apps that were updated alongside macOS (Safari, Mail, Messages) migrate their data. The first launch of each is slow; the second is normal.

All of this competes for the same disk and the same processor cores, which is why a superuser answer from 2017 still holds: "One major cause of slowness after a major macOS upgrade is a bunch of system processes contending for disk access as they update their databases." The answer to an update slowdown is time, not tools.

What the first 48 hours look like

How to confirm it is settling and not broken

Open Activity Monitor, click the CPU tab, and click the % CPU column header so the busiest process is at the top. For the first day after an update you should see some combination of mds_stores, mdworker, corespotlightd, photoanalysisd, mediaanalysisd, bird and cloudd up there, each anywhere from 20 to well over 100 percent (a process can use more than one core).

That is the signature of a settling update. Three more checks:

• Spotlight shows it is indexing. Click the search icon in the menu bar and type anything. If a progress bar or "Indexing" appears, the index is still being rebuilt.
• The numbers fall over time. Check again in a few hours. Settling means the same processes are lower, or gone from the top. Broken means something new is at 100 percent and stays there, or memory pressure is red for hours.
• The Mac is fast when those processes are idle. Late in the evening, if nothing is at the top of the CPU tab and the Mac still feels slow, the update is not the cause.

What does not count as settling: one third-party app at 100 percent CPU for hours after the update. That is an app that needs its own update to work with the new macOS, and quitting it (⌘Q, or Force Quit if it will not respond) brings the Mac back immediately. Check the developer's site for a compatible version.

A less-known tell: the Activity Monitor Memory tab. Indexing and analysis use memory while they run, so memory pressure may be yellow for a day. If it is red, or if the Mac warns about running out of application memory, that is a separate problem worth its own look.

What to do, in order

1. Plug the Mac in

   Photos analysis only runs on power, and Spotlight runs faster when the Mac is not throttling to save battery. Connect the charger and leave it.

2. Leave it awake overnight

   Keep the lid open, or connect an external display, and let the Mac sit at the login screen or desktop overnight. Turn the display brightness down. The heavy jobs run while it is idle and awake.

3. Do not restart repeatedly

   A restart interrupts indexing and it resumes from where it left off, but every restart costs a few minutes of restart work. One restart after the update is fine. Five are not helping.

4. Do not reinstall macOS or run a cleaner

   Reinstalling starts the whole 48 hours again. Cleaners that "rebuild Spotlight" or "clear caches" do the same. The caches are the thing being rebuilt.

5. Update your apps

   Open the App Store and check for updates, and check any apps installed outside the store. An app built for the previous macOS can misbehave on the new one and hold a core at 100 percent.

6. Check again on day 3

   Open Activity Monitor, CPU tab. If the indexing and analysis processes are no longer near the top and the Mac is still slow, move on to the general checklist on why is my Mac so slow.

Sequoia, Tahoe and older: does the version matter?

Every major version (Sonoma, Sequoia, Tahoe) produces the same first-48-hours pattern, because every major version triggers the same rebuilds. What changes between versions is which job is biggest. Sequoia and Tahoe added more on-device analysis for Photos and Apple Intelligence features, so mediaanalysisd is a larger share of the settle than it used to be. On Tahoe, a fresh pass over the Photos library can take much of a night on a large library. 9to5Mac's advice for the Tahoe case is the same as this page's: connect to power overnight and let the machine get on with it.

Minor updates (15.4 to 15.5, say) usually trigger a smaller settle: a security scan, a partial Spotlight refresh, app cache rebuilds. An hour or two rather than two days. If a minor update leaves the Mac slow for a week, look for a third-party app that broke rather than blaming the update.

Intel Macs and Macs with a hard disk instead of an SSD take longer at every step, because indexing is disk-bound. An older Intel MacBook with a 500 GB spinning disk can take several days to settle. There is no shortcut except leaving it on and plugged in.

When the update is not the cause

Give it 48 hours plugged in. After that, it is worth worrying when:

• Nothing is busy and it is still slow. If the CPU tab shows only idle processes and the Mac still drags, check free disk space first. A Mac with under 10 percent free space is slow regardless of updates, and updates themselves take space. Free up space before anything else.
• One process never settles. mds_stores still at 100 percent after three days plugged in usually means a folder it cannot finish indexing (a huge mail archive, a disk image, a network volume). Adding that folder to Spotlight's privacy list (System Settings, Spotlight, Search Privacy) lets the rest of the index finish.
• The Mac is slow and hot with the fan on constantly. After the settle, that points at an app or at WindowServer, not at indexing.
• Memory pressure stays red. Indexing uses memory temporarily. Red pressure after the settle means an app is leaking or you simply have too much open.

In every one of those cases the fix is an app, a setting or free space, and none of them are made better by reinstalling macOS. Reinstalling is the one thing that guarantees another 48 hours of exactly what you are trying to escape. If you would rather not watch Activity Monitor by hand, Safe to Quit tracks each process over hours and tells you whether the busy one is an update settling or something that has stayed busy long past when it should have finished.