Recover Lost Mac Files After Migration Assistant
If Migration Assistant finished but your files are missing, they are usually still on the source Mac or in a hidden folder on the new one. You can recover them by re-running the migration from the source, checking the Migration Assistant log for skipped items, or using a recovery tool if the files were overwritten. This guide walks through each method in order of safety and likelihood of success.
Why Migration Assistant Loses Files
Migration Assistant copies user accounts, applications, settings, and documents from an old Mac, a Time Machine backup, or a Windows PC. The process is generally reliable, but files can go missing for several concrete reasons:
- Insufficient disk space on the destination Mac – the migration stops or skips large files silently.
- User chose a subset during the selection screen – it is easy to uncheck a folder like Pictures or a whole user account without noticing.
- App incompatibility – some third-party apps are skipped and their associated data folders (in ~/Library/Application Support) are not copied.
- Permissions errors – files that cannot be read on the source are skipped.
- Interrupted transfer – a sleep, disconnect, or power loss can leave the copy incomplete.
Understanding the cause matters because it determines whether the files are still on the source (easy), in a partial state on the destination (recoverable), or gone entirely (needs a backup or recovery tool).
First: Check the Migration Log
Before trying anything else, look at what Migration Assistant actually did. macOS writes a log of every item it copied and every item it skipped.
- Open Console (in /Applications/Utilities).
- In the search field, type MigrationAssistant.
- Look for entries with the word Error or Skip.
- Note the exact file paths mentioned – they may point to where files were placed or why they were skipped.
Common log messages include “Failed to copy� (permissions or disk full), “Skipped because item is in use�, and “No such file�. If the log shows a file was skipped, you can manually copy it from the source Mac using a USB drive, network share, or a direct Thunderbolt cable.
Re-run Migration Assistant (Safest Option)
If the source Mac is still available and unchanged, the simplest fix is to run Migration Assistant again. It is designed to merge data, not overwrite everything, so re-running it will add missing files without deleting what already transferred.
- On the new Mac, open Migration Assistant (in /Applications/Utilities).
- Choose From a Mac, Time Machine, or startup disk.
- Connect the source Mac the same way as before (Wi-Fi, Ethernet, Thunderbolt, or a Time Machine backup).
- When the list of items appears, expand Your Information and check every box – especially the user account and its subfolders.
- Let it run again. It will copy anything that is missing or newer.
This works because Migration Assistant compares timestamps and file sizes. It will not replace a file that already exists unless the source version is newer. If the first attempt failed due to low disk space, free up space on the destination first (see the next section).
Free Up Space and Check Hidden Folders
A full disk is the most common cause of incomplete migrations. Before re-running, check how much free space you have:
- Click the Apple menu → About This Mac → Storage.
- You need at least as much free space as the total size of the data you are migrating, plus a few GB for temporary files.
- Delete caches, old downloads, or move large media to an external drive to make room.
Sometimes files are actually on the new Mac but in an unexpected place. Check these locations:
- /Users/Shared/ – Migration Assistant sometimes places files here if the original user folder could not be created.
- /Users/<username>/Migration – a temporary folder that should have been cleaned up, but may remain after a crash.
- ~/Library/Containers – app-specific data for sandboxed apps may be under a container folder, not in Documents.
Use Finder’s Go → Go to Folder (Cmd+Shift+G) and type each path to see if your files are there.
Recover from Time Machine or an External Backup
If the source Mac is gone or already erased, your next best bet is a Time Machine backup. If you backed up before migrating, the files are almost certainly there.
- Connect the Time Machine drive to your new Mac.
- Open Time Machine from the menu bar (or System Settings → General → Time Machine).
- Browse to the date before the migration.
- Find the missing folder or file, select it, and click Restore.
If you do not have a Time Machine backup but have a clone made with a tool like Carbon Copy Cloner or SuperDuper, mount that clone and copy the files directly. If you have neither, skip to the next section.
Use Data Recovery Software as a Last Resort
If the files were overwritten or the source disk was reformatted, recovery software may be able to find them. These tools scan the raw disk for file signatures and rebuild deleted files. They work best when you stop using the disk immediately – every new write can overwrite the data you are trying to recover.
- Download a reputable recovery app (e.g., Disk Drill, Data Rescue, or PhotoRec – the last is free and open-source).
- Install it on a different disk than the one you are recovering from, if possible.
- Run a deep scan on the source disk or the destination disk where the files should have been.
- Preview the found files before paying for a license – most tools let you see filenames and thumbnails for free.
Recovery software works best for documents, photos, and videos. It rarely recovers app data that was stored in SQLite databases or plist files, because those are fragmented. Also, if the disk has been used heavily since the loss, recovery chances drop quickly.
Prevent This in Future Migrations
The best fix is to avoid the problem next time. Before any migration, do the following:
- Back up both Macs – Time Machine on the source and a separate backup of the destination if it has data.
- Check disk space on the destination – it must have more free space than the total data size.
- Use a wired connection – Wi-Fi migrations are slower and more prone to interruption.
- Disable sleep on both Macs during the transfer (System Settings → Battery → Options → Prevent automatic sleeping).
- Do not use the destination Mac while migration is running – opening apps can interfere.
- Verify after migration – spot-check a few folders and use the Migration Assistant log to confirm nothing was skipped.
Frequently Asked Questions
Q: I migrated from a Time Machine backup, but my files are not on the new Mac. Can I get them back?
Yes. Connect the Time Machine drive to the new Mac and use Time Machine to browse to the backup date. If the backup itself is incomplete, try a recovery tool on the Time Machine drive, but note that Time Machine stores files in a sparse bundle that recovery tools often cannot read directly.
Q: Migration Assistant says “completed successfully� but my Photos library is missing. Why?
Photos libraries are large and often stored in the Pictures folder. If you unchecked Pictures during the migration, it would be skipped. Check the log for “Pictures�. If it was copied, look for Photos Library.photoslibrary in ~/Pictures – if it is there, double-click it to open. If not, re-run migration and make sure Pictures is checked.
Q: Can I recover files that were overwritten by a second migration?
Yes, but only with a data recovery tool, and only if the overwritten blocks have not been reused. The more time passes and the more you use the Mac, the lower the chance. Stop using the disk immediately and run a deep scan.
Q: How do I know if my files are on the source Mac still?
If you have not erased the source Mac, connect it to the new one via target disk mode (hold T at startup) or a network share, and browse the user folder. If the files are there, copy them manually or re-run Migration Assistant.
Q: Will re-running Migration Assistant delete files that already transferred?
No. It only adds missing or newer files. It does not remove anything from the destination. It may ask about conflicts for files with the same name – choose “Keep Both� to be safe.
Q: Is there a free way to recover lost files without software?
If you have no backup, the only free method is to check the Migration Assistant log and the hidden folders mentioned above. If the files are not there, you will need a recovery tool – PhotoRec is free, but it is command-line based and recovers files without original names.
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