Mac slow after migrating with Time Machine: why and how to fix it
A new Mac, your account moved from the old one, and ever since everything is slower: Privacy & Security takes seconds to open, apps hesitate. Yet a new user is lightning fast. Here is why it happens and how to fix it without starting over.
Short answer: after Time Machine or Migration Assistant your account carries permissions, startup items and preferences from the old Mac. macOS keeps checking them for nothing and slows down, while a new user is fast because it doesn't have them. You can fix them by hand from Terminal, or with Revive, free, which finds them in seconds, repairs them in one click and backs everything up first.
The test that settles it
First make sure the problem really is your account and not the Mac. Go to System Settings › Users & Groups, create a test user, log in with it and open the same apps and Privacy & Security.
- If everything is fast with the new user, your migrated account is the culprit: read on.
- If it's slow there too, the slowdown comes from something else (an almost full disk, heavy apps, hardware issues) and repairing the account won't be enough.
What a migrated account carries over
| Leftover | Where it lives | Effect |
|---|---|---|
| Privacy permissions of apps that are gone | the TCC database in ~/Library/Application Support/com.apple.TCC | Privacy & Security slow to open |
| Broken startup items | ~/Library/LaunchAgents | macOS tries to launch programs that don't exist |
| Preferences tied to the old hardware | ~/Library/Preferences/ByHost | useless settings and possible conflicts |
| The old Mac's keychain | a folder named after the other Mac's UUID in ~/Library/Keychains | a keychain this Mac can't use |
| Files owned by another user | your home folder | permission errors in apps and updates |
| Damaged preferences | ~/Library/Preferences | apps trying to open unreadable files |
Checking them by hand in Terminal
These commands only look, they change nothing. Always back up before deleting or moving any file.
Your user's startup items, to see whether they point to programs that are gone:
ls ~/Library/LaunchAgents
launchctl list | grep -v com.applePreferences and keychain from the old Mac: compare this Mac's UUID with the ones in the file names.
system_profiler SPHardwareDataType | grep UUID
ls ~/Library/Preferences/ByHost
ls ~/Library/KeychainsFiles in your folder owned by another user:
find ~ -not -user "$(whoami)" 2>/dev/null | headDamaged preferences:
plutil -lint ~/Library/Preferences/*.plist | grep -v ': OK'For privacy permissions of apps that are gone you can reset a single app's permissions with tccutil reset All app.bundle.id, but finding which ones are orphaned means reading the TCC database, which macOS protects. It's the most awkward part to do by hand.
The easy way: Revive
Revive runs the same checks in seconds without changing anything, then shows what it found in plain words, with a label telling you how much you'll gain. You repair in one click and, before touching anything, Revive saves a backup: you can undo everything from the history whenever you like. It doesn't delete documents, photos or mail and it isn't a "cleaner". After the repair, restart your Mac.
It's free and runs on macOS 14 Sonoma or later, on Apple silicon and Intel Macs.
Frequently asked questions
Why is my new Mac slower than the old one?
Often it isn't the Mac but the migrated account: Time Machine and Migration Assistant also copy permissions and settings tied to the old computer, which macOS keeps checking for nothing. The test is a new user: if it's fast there, the account is the problem.
Do I have to create a new user?
No. You can repair the leftovers in the account you already have, by hand or with Revive, without copying files and settings again.
Will repairing my account delete my files?
No, as long as only configuration files are touched. Revive never touches documents, photos, music or mail and saves a backup before every repair.
Why does Privacy & Security take so long to open?
Usually because of permissions left over for apps that aren't on the new Mac anymore: macOS checks them one by one every time you open the panel.