Block syncing of specific file types
You can prevent users from syncing specific file types when they sync their OneDrive for Business files.
To block syncing of specific file types
Open the OneDrive admin center, and click Sync in the left pane.
Select the Block syncing of specific file types check box.
Type the file name extensions you want to block, for example: exe or mp3.
Do not include the periods with the extensions, or any other punctuation, spaces, or special characters.
Click Save on the Sync page.