M365 Changelog: (Updated) Changes in file open behavior in classic Teams

MC709269 – Updated April 3, 2024: Microsoft has updated the content below with additional information regarding the Guest user experience. Thank you for your patience.

Microsoft is making changes to the file open experience in Teams that will affect users in select scenarios. These changes are part of our ongoing security enhancements and optimizations to provide you with the best possible collaboration platform.

When this will happen:

Beginning in late February 2024 and completing by late March 2024, on classic Teams version >1.6.00.34970

How this affects your organization:

The following changes will take effect:

• All files in Shared channels will now open in browser instead of within Teams. This will ensure that you can access all the latest features and functionalities of the web app. 
• OneNote notebooks pinned to channels/chats or the Notes tab within channels will continue to open within Teams. However, OneNote files when launched from any other surface in Teams will open in browser. This is a temporary situation for a few weeks until Microsoft integrates latest file open behavior into the OneNote Teams app, at which point you can go back to working with these files within the Teams environment.
• Some Word, Excel, and PowerPoint files that are pinned as tabs on chats/channels using the “Make this as tab” feature will render in read-only mode due to the legacy viewer powering the experience. Users will be asked to re-pin those documents as tabs to get an edit-ready experience powered by the latest viewer app for a more secure experience.
• For users on classic Teams version older than 1.6.00.34970, files in the above scenarios will open in read only mode.

Note: Guest users will have a read-only view of files that are opened within Teams. For an edit experience, they will need to open files in browser. On the new Teams, guest users will directly land in an edit-ready experience in the browser.

What you can do to prepare:

• Microsoft recommends upgrading to new Teams or to 1.6.00.34970 and above versions of classic Teams.
• You may consider updating training and documentation as appropriate.

Microsoft apologizes for any inconvenience this may cause and appreciate your understanding and cooperation. If you have any questions or feedback, please contact us at filesteamsfeedback@microsoft.com