Consider the following scenario:
On a SharePoint Online site, you have a Promoted Links list.
In the Promoted Links list, you create a link to a local file that uses the file:// protocol.
However, when you view the Promoted Links list in the tile view and then click the link that you created, you receive the following error message:
This is the expected behavior in SharePoint Online. This issue occurs because the file:// protocol isn’t supported for local files in the Promoted Links list. The http:// and https:// protocols are supported in the Promoted Links list in SharePoint Online.
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