Why does DropBox occasionally add *com.dropbox.attributes files?

Question

I've been a user of Dropbox for a few years now. Just recently I noticed that files with the extension com.dropbox.attributes started to appear in some dropbox sub-folders.

Steps

1. I create a new directory in dropbox with the intention of adding some image files.
2. I add the image files to the new directory
3. The files begin to sync and then new files start to appear with the same names of the files I'm syncing but appended with the extension com.dropbox.attributes. Each of these additional files is ~160 bytes.
4. These com.dropbox.attributes files are also visible in the DropBox.com web client. And they sync to other machines with the same dropbox account.

Example: I'll add: IMG_1195.JPG a 1.6MB file. And then the following will appear seconds later: IMG_1195.JPG/com.dropbox.attributes at 160 bytes. And the contents of this new file is a bunch of hexadecimal values.

Why is this? How do I make it stop?!

It's very noisy.

Solution

Well, for completeness’ sake, here’s the official take on this:

These files are from a filesystem incompatibility somewhere on one of your linked devices (or on one of the linked devices belonging to one of the members of one of your shared folders). Some filesystems like HFS (OS X) and NTFS (Windows) are capable of assigning "extended attributes" (xattrs) to files and folders (for things like the tags you can apply in Mavericks/Yosemite).

The issue arises when files with these extended attributes are copied to a filesystem that doesn't support them (such as FAT or FAT32, which are often found on old hard drives, USB sticks, and some other external drives). These filesystems can't store extended attributes, so Dropbox puts those extended attributes into new ':com.dropbox.attributes' files, so as not to lose any data.

To test if these files are still being created, could you create a test file on a Mac, then add a tag to the file (see e.g. http://support.apple.com/kb/HT5839)? If you see another "com.dropbox.attributes" appear for this file, go to the Dropbox website, right-click on it, and choose 'View previous versions' to see which user is creating these files, and on which device.

If you do not see a new "com.dropbox.attributes" file appear for this test file, it could be the case that these files were created during a single event, such as when files were moved from a drive that doesn't support xattrs, so you can just delete them.

tl;dr: You can most likely remove them entirely without causing any problems.

Comments

[Daniel B]

Are you, by any chance, using OS X?

[Michael R]

@DanielB Yes, I am using OSX. I have a dropbox account linked on OS X Mountain Lion, OS X Lion and Windows 7.

[Cfinley]

Whilst this may theoretically answer the question, it would be preferable to include the essential parts of the answer here, and provide the link for reference.

[Michael R]

I'm not so much interested in deleting them, than preventing these com.dropbox.attributes files from appearing.