Introducing New Capabilities for File Viewer in Microsoft 365

emvaleri Since rollout of the new File Viewer, which is very slowly rolling out user by user over the last week, we are experiencing critical disruptions in our business processes.

Microsoft has initiated the rollout of the new "File Viewer in Microsoft 365" within our M365 tenant. This change is reflected visually by the background color of the File Viewer transitioning from white to black.

In a standard "All Documents" view in SharePoint Online, users can normally preview files using the breadcrumb menu and the "Preview" function. Navigating through files in the File Viewer operates smoothly under these circumstances.

However, when users, who have the new File Viewer activated, operate within more complex document library views (e.g., views where files are displayed without folders), a critical issue arises:

• Users are unable to navigate through all files in the document library via the File Viewer.
• After previewing the second or third file, the File Viewer hangs.
• The browser’s URL field exhibits continuous switching between URLs of two files, refreshing every second.
• This behavior makes the browser unusable.
• Eventually, users are expelled from SharePoint due to excessive server activity, triggering SharePoint's throttle functions.

This disruption in the ability to preview and scroll through files in document libraries impacts a critical business process, specifically the editing of file metadata in sequence.

Steps Taken to Contain the Issue:

1. Browser Change: Attempted accessing SharePoint using different browsers (e.g., Chrome, Edge, Firefox).
2. Different Document Libraries: Tested the functionality in various document libraries to rule out specific library issues.
3. Permission Adjustments: Granted full permission levels to users experiencing the issue to check for any permission-related discrepancies.

Please advise. We were so far not able to escalate the support ticket. The reported problem within "Service Health" in the admin-area has been closed without any finds. We can narrow the incident down to the new file viewer, since users with still the old file viewer do not experience these problems.