Both Box Sync and Box Drive will not sync files that the program ignores or blocks. Ignored files include invisible in Windows Explorer or Finder, such as temporary or system files. Blocked files include file types that Box Sync or Box Drive does not recognize.
Box Sync still requires read permissions on these files in order to determine if the file should be blocked or ignored during the scanning process.
Box Sync and Box Drive ignore the following file types and shortcuts:
Temporary files and folders (.tmp and files starting with the ~ character)
Backup copies of files (.bak)
System and hidden files (hidden folders are synced but hidden files are not synced: such as ._dstore, desktop.ini, thumbs.db).
File names that start with a dot "." are considered hidden files.
Shortcuts created via Windows Explorer or Finder
Hard links (a file that has multiple directory entries associated with it will not be synced)
File names that are exactly 8 uppercase hexadecimal digits (0,1,2,3,4,5,6,7,8,9,A,B,C,D,E, or F) with no extension – for example: 1234AD38 or ABE32BD0.
File names containing special characters
Web based documents (such as .gdoc, .gsheet, and bookmarks) will not sync to the Box Sync folder, excepting Box Notes which will be synced to the Box Sync folder, and will open in your browser.
Box Sync and Box Drive block the following file types:
These file types can be uploaded and stored in Box via the Box web site, but Box Sync will not recognize them. They will not be synced even if they are in a synced folder.
Box Sync will sync folder names ending in a dot ("."), but users on Windows computers will not be able to access the folder. Users will see an error dialog "Location is not available". Please remove the dot "." from the end of the folder name, or Windows users will be required to access the folder only from the Box web site.
Box Sync and Microsoft Access database files (.accdb and .mdb):
Due to the saving behavior of Microsoft Access, it's extremely likely that Box Sync will create duplicate copies of .accdb and .mdb files if multiple users are syncing the same file from Box.
We do not recommend having multiple users sync the same .accdb or .mdb file.
Box Sync and Microsoft OneNote Notebooks:
Microsoft does not recommend using synchronization programs like Box Sync with OneNote notebooks:
"In general, OneNote notebooks should always be synced and moved by the OneNote application, and not by file based synchronization systems such as a client application"