The Sync feature allows users to download a copy of a document library, and access the file offline. This feature is ON by default, and to turn it off, follow the steps below:
Note: you will need to be a Site Collection administrator to do this.
- Go to Site Settings
- Find Search and offline availability under heading Search
- One the Search and offline availability page, select No against Offline Client Availability.
- Press OK.
The Sync icon is disabled in all of the libraries in this site collection.