Why are there files starting with ._ created when copying files to an external drive?

Last modified date: 2024-03-27

Applicable Products

QTS, QuTSHero

Scenario

When files are copied to an external USB drive, a new file with prefix "._" is created on the destination, together with the file that was copied.

Details

When files on the NAS are accessed by a MAC computer via SMB or AFP, macOS may add additional information to the files as "extended attributes". External USB drives with file systems such as FAT32, exFAT, and NTFS does not support these extended attributes, thus these extended attributes are separated and saved under a new file of the same name as the original files, but with the prefix "._".

These files will not affect the original file and can be deleted manually.

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