What Is Lost and Found on a Mac?

If a file marked lost+found suddenly appears on your Mac, better back up your system as a precaution.
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The lost and found folder (named "lost+found") in Mac OS X is not a place for missing items, but rather a place where orphaned files live. If you stumble across this strange looking folder, don’t panic, but don’t delete anything either, as files here could be vital to the health of your computer system.

1 The Lost and Found Folder

Computers perform best when there is order; anything unusual can throw them off. The Mac likes to be turned on and off the same way each time. If you shut down your computer improperly, or if you lose power that causes a sudden shutdown, you may reboot to discover a mysterious folder on your hard disk called lost and found, specifically "lost+found." This lost+found is your Mac OS's underlying UNIX at work. The lost+found is where Unix dumps orphaned files that it doesn't know what to do with.

2 Can I Delete the Folder?

You might be able to delete the contents of the lost and found folder, but it is not advisable -- especially if you don’t know exactly what is in it. Files and programs that are key to running your operating system could be in the lost and found folder; your Mac may not run if you delete or move any of these files, so handle them with caution.

3 Exploring the Folder

It’s a good idea to look in the lost and found folder, provided you don’t remove or move any of its contents. If the elements and files inside the folder are very old and your computer is running smoothly, chances are that the folder does not indicate current problems with your system. However, if several recently dated documents are in the folder, there could be serious issues brewing with your Mac’s hard disk.

4 Run Diagnostics

If your lost+found folder appears on your hard disk and contains new files, you may have a serious issue. If the lost+found folder suddenly appeared for a reason other than an abrupt shut-off, your computer is probably experiencing other problematic symptoms, such as running very slowly, rebooting for no reason or not responding consistently to commands. If you have questions about the health of your hard disk, run Mac's built-in Disk Utility. If the Disk Utility doesn't identify any issues but your computer is still not running smoothly, use a third-party tool recommended by Apple, such as Alsoft DiskWarrior, Symantec’s Norton Disk Doctor or Micromat TechTool. Even if the lost+found folder turns out to pose no serious problem, it’s a good idea to regularly back up your data.

Bonnie Crowe is a mother of two teenagers; a teacher and author of children's books, curriculum and articles on English grammar, literature, technology, art, parenting and career guides for high schoolers. She's a former director of AOL Parenting, a member of SCBWI, and a graduate from the University of California,Berkeley.