Mac Slow After a macOS Update? It Usually Fixes Itself in 48 Hours
“My Mac got noticeably slower after updating macOS”
Being slow for the first 24 to 48 hours is normal — the system is rebuilding indexes and re-analysing your photo library. Only start troubleshooting if it is still slow after three days.
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Give it a day or two, keep it plugged in, and do not force a shutdown. Meanwhile check Activity Monitor for mds_stores or photoanalysisd — if they are running, the rebuild is progressing normally.
What you are seeing
- Boot and app launches are slower after the update
- Spotlight returns no results or is very slow
- Fans spin up and temperatures rise
- Sections of System Settings take a long time to load
Common causes
- Spotlight rebuilding the full-disk index
- Photos library running face and scene analysis
- iCloud re-syncing data
- Older software incompatible with the new system, failing and retrying in a loop
- The new macOS simply demanding more from older hardware
Full walkthrough
- 01
Confirm it is index rebuilding
Open Activity Monitor. If you see mds_stores, mdworker or photoanalysisd using significant CPU, the system is rebuilding indexes and analysing photos. This runs from a few hours up to two days and is expected behaviour — do not interrupt it.
- 02
Find incompatible legacy software
Every major release retires a batch of older apps. Check System Settings → General → Login Items for erroring entries, and Activity Monitor for processes that keep crashing and restarting. Removing or updating them resolves most slowdowns.
- 03
Force a Spotlight reindex
If the index is clearly stuck — search returns nothing for a long time — rebuild it manually. It is time-consuming, so run it overnight.
sudo mdutil -E /⚠️ Heads upRebuilding keeps the machine under heavy load for several hours. Run it when you do not need the computer. - 04
Clean up login and background items
Startup items carried over from the old system can misbehave. Disable them one by one in Login Items and restart to see whether things improve. This alone fixes a good share of post-update slowdowns.
- 05
Check available disk space
System updates consume extra space. If the drive is nearly full, swap pressure increases and everything feels sluggish. Keep at least 20% free.
df -h / - 06
Reinstall as a last resort
If it is still slow after several days and you are confident the system itself is at fault, use Recovery Mode to reinstall macOS while keeping your data. Downgrading requires a bootable installer you prepared in advance, so back up first.
⚠️ Heads upComplete a full Time Machine backup and verify it is readable before reinstalling.
How to prevent it
- Always back up before a major version upgrade
- Check that your essential apps support the new release beforehand
- Never upgrade in the middle of a client project
Follow-up questions
How long until it settles down?
Typically 24 to 48 hours. If it is still clearly slow after three days, work through software compatibility and disk space.
Should I update an older Mac?
On machines five or six years old, the visual effects and background services of a new release cost more than they return. Unless you need a specific feature or security fix, staying on a stable version is reasonable.