Guide
The ._ files on your Android phone, and how to stop them
Copy music or photos from a Mac and a twin appears for every file, starting with a dot and an underscore. They are harmless, they are not copies, and they are easy to get rid of.
You copied an album from your Mac to your phone, or filled an SD card in a card reader. Now the music player lists every track twice, once as Track 01.mp3 and once as ._Track 01.mp3, and the second one will not play. The gallery shows grey squares. A file manager shows a 4 KB file next to every real one.
Those are AppleDouble files. Your Mac wrote them, and nothing is wrong with your phone.
What a ._ file is
A file on a Mac carries more than its contents. macOS attaches extended attributes to it: a Finder tag, the web address a download came from, the quarantine flag behind Gatekeeper's "Are you sure you want to open it?", and for some older files a resource fork. APFS, the Mac's own file system, keeps all of this inside the file system, out of sight.
FAT32 and exFAT cannot keep any of it, and those are the formats of nearly every SD card and USB stick. So when macOS copies a file to one of them, it puts the attributes in a separate file next to it, named with ._ in front of the original name. That sidecar is the AppleDouble file. It is usually exactly 4,096 bytes, whatever the size of the file it belongs to.
The Mac hides any file whose name starts with a dot, so on the Mac you never see them. Android hides them in some places and not in others. File managers list them once hidden files are shown, and music players and car stereos that read folders themselves often try to play them.
How they reach the phone
| How the files got there | Leaves ._ files | Leaves .DS_Store files |
|---|---|---|
| SD card or USB stick filled on the Mac | Yes, one per file | Yes, in folders opened in Finder |
| An MTP app, such as Android File Transfer or OpenMTP | No, MTP sends only the contents | Only if the folder you copy has one |
| The phone mounted in Finder with SideMount | No, refused on the phone | No, refused too |
The card reader is the usual source. Fill a card on the Mac, put it in the phone, and every file you copied has a twin. Folders you opened in Finder also get a .DS_Store file, which holds the window's view settings.
Are they safe to delete?
Yes. A ._ file holds only the Mac's metadata about the file next to it, never the file's contents, and nothing on the phone reads it. Deleting one loses the Finder tag or the download address, which only a Mac would ever use.
Look before you delete, though. A real file can start with ._ too, rarely, so list them first and check the list is what you expect.
How to remove them
From an SD card or USB stick, on the Mac
With the card mounted, open Terminal and list them, with the card's name in place of CARD:
find /Volumes/CARD -name '._*' -type fIf the list looks right, delete them:
find /Volumes/CARD -name '._*' -type f -deletemacOS also has a tool of its own for this, dot_clean. Run as dot_clean -m /Volumes/CARD, it merges what it can back into the files and then deletes every ._ file.
From the phone itself
With USB debugging on and adb installed, the same two steps work on the phone's storage:
adb shell find /sdcard -name '._*' -type f
adb shell find /sdcard -name '._*' -type f -deleteWithout a computer, a file manager on the phone can delete them by hand once it shows hidden files. A search for ._ finds them all.
How to stop them coming back
No setting stops macOS writing ._ files to a FAT or exFAT card. What you can change is what you copy, or how.
- Copy without the attributes. In Terminal,
cp -Xcopies files without their extended attributes, so there is nothing for a sidecar to hold. Finder always copies them. - Strip them first.
xattr -cr ~/Music/Albumremoves every extended attribute from a folder before you copy it. The files themselves do not change. - Copy over the cable instead of with a card. An MTP app sends only the contents of each file. SideMount mounts the phone in Finder and refuses
._and.DS_Storefiles on it, so a Finder copy arrives clean.
With SideMount, Finder can still read and write tags on the phone's files while it is mounted. The attributes stay on the Mac, in memory, and are dropped when you eject the phone, which only ever gets the files. The setup guide covers the first connection, and every way to move files between Android and a Mac compares the routes.
Questions
Why is every ._ file 4 KB?
An AppleDouble file is a small header with room for the attributes, and macOS writes it as one 4,096 byte block, whatever the size of the file it belongs to. One that carries a large resource fork can be bigger.
Will deleting them damage my photos or music?
No. The photo or the track is the file without the ._ in front. The sidecar only holds Mac metadata such as Finder tags, so the phone and its apps lose nothing.
Does Android File Transfer create ._ files?
No. MTP, the protocol it uses, sends only each file's contents, so there is nothing to put in a sidecar. The ._ files come from a card or a drive that the Mac mounts. Google no longer offers Android File Transfer, though: see what replaces it.
Do Finder tags stay on a phone mounted with SideMount?
While it is mounted, yes. SideMount keeps tags and other attributes on the Mac, in memory, so Finder works as usual. They are gone once you eject the phone, because the phone itself never stores them.
