How to fix issue related to Open With Explorer option in SharePoint Online

Sriram Varadarajan
Enterprise Architect
Published On :   17 Apr 2016
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Simultaneous upload to different document libraries in SharePoint Online may lead to failure of upload in most cases. In this article we can see how to reproduce and fix this Open With Explorer issue in a Windows 7, 64 bit machine with IE 11.

Scenario and steps to re-produce

We have multiple SharePoint Online sites and and we are using the "Open with Explorer" option for managing files in our SPO Team site libraries. We face intermittent upload issues in these sites and upon investigation we came to know that this is related to issue related to legacy WebDav protocol.
To reproduce the issue,

Open  two different SPO libraries in two different "Open with Explorer" windows on your PC and copy/paste of files between these two windows.
Copy/ Paste works sometimes but drag/drop fails with the below Windows Security Message

These files might be harmful to your computer.
Your Internet Security Settings suggest that one or more files may be harmful. Do you want to use it anyway ?
->You Click "Ok" and see the below error:
Error:  "Move: Can't read from source file or disk."

It Doesn't work even after "Try again" is clicked.

Fix for this issue
Add the following sites to Internet Explorer Trusted Sites list:
Ensure all the O365 Endpoints are opened in your network as mentioned in the article:
Ensure the "Webclient" windows service is ENABLED and is set to start automatically every time a PC starts.
The UsePersistentCookiesForExplorerView parameter for the Set-SPOTenant cmdlet that's used in the SharePoint Online management shell lets SharePoint issue a special cookie that will allow this feature to work even when Keep Me Signed In isn't selected.
After this parameter is enabled, you are prompted when you click Open with Explorer in SharePoint Online by a dialog box. After you click "This is a private computer", the persistent cookie is stored.

Issue with respect to Drag and Drop
The error message what we get is a generic error, it is not the exact message what we receive from the failed component.Currently the legacy WebDAV protocol is not capable of doing such operations and communications.

Intermittent Copy / Paste behaviour
MS is not recommending to use OPEN WITH EXPLORER to move the content as it uses legacy protocol in the background and also it depends on user’s cookie information. The alternative is to use One drive

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