Need to understand why so many files fall under Not Allowed when syncing

Trying to perform a sync of over 10,000 files to OneDrive for Business with ODrive. When using a Windows machine I am seeing over 1500 files failed to sync. On a Mac the number is closer to 500. The error reads in part the file name is not allowed and there is a “+” in the file name however several files uploaded successfully with a “+” in the name.

The error message can be viewed here:

I hope to understand the limitations with Windows as well as Mac.


Hi Allan,
Can you submit a diagnostic from both the Windows machine and the Mac (from the odrive tray menu)? OneDrive for business has a large amount of restrictions on characters, length, file type, number of files, etc. It is possible that something other than an illegal character is being hit, so I want to make sure. A “+” should actually be fine. It looks like OD4B is rejecting it for another reason.


Diagnostics from both machines has been sent.


Ahh, I missed this before. The file can’t be uploaded because the folder it is in has an illegal character (&). Can you try removing the illegal characters from the parent directories first, then we can see where it settles?


I can certainly try removing the “&” however there are 1197 other files that successfully uploaded to the same parent directory. I would have thought that either all would upload or none would upload.


Actually, you are right “&” is not an illegal character for Sharepoint Online (OD4B), but is for Sharepoint 2013. Their restrictions are confusing. I actually can’t tell right now why, exactly, they are preventing these files. I am speculating that it may be path length related, but I need to experiment more to determine exactly.

So after a little bit of head scratching I figured out that OD4B will not allow a “&” in the file name on upload. It does, however, allow you to rename a file to a name with “&”. It will also allow a folder with a “&” in the name. :rage:

The bottom line is that you will need to remove the “&” characters if you want to upload to OD4B.

I have dealt with onedrive synch issues though ou the years. This has nothing to do with odrive. My best advice is find some way to not use onedrive. Its just not worth all the hassle. Dropbox seems to be the most forgiving.