In line with the change to Stream videos storage to OneDrive and SharePoint. Microsoft are now enabling the ability to control the download functionality on shared videos. Previously, when sharing documents from OneDrive or SharePoint Online, users had the ability to make a file read-only and restrict download at the time of sharing.
Planned for late October for targeted release tenant and November for all other tenants, this feature should be available to everyone by the end of November. Once enabled, when sharing a video from OneDrive or SharePoint Online, users will have the ‘Block Download’ option. This option will ensure that recipients of the sharing link can only view the video in the web browser via the OneDrive web previewer.
While it’s not recommended for most use cases, this option can be disabled on a site or tenant level via the below commands in the SharePoint Online Management Shell respectively:
Set-SPOSite -Identity <Site URL> -BlockDownloadLinksFileType:$True