Teams Upgrades File Sharing to be Consistent with Office 365

File Sharing Based on Sharable Links

Microsoft originally announced that Teams would have a new file sharing experience in Office 365 notification MC218732 on 16 July 2020 (Microsoft 365 roadmap item 51230). As is sometimes the case, the roll-out was delayed and is now due to complete in late September 2020.

Update (September 3): Microsoft report that they have paused the roll-out of the feature to make some additional code changes. They will issue a further update when the roll-out resumes.

Referring to the update as a new files sharing experience is a stretch. What’s really happening is that Teams is adopting the common file sharing dialog that’s already used in OneDrive for Business, SharePoint Online, and OWA. It’s part of an effort to achieve consistency in sharing behavior across Office 365 announced at the Microsoft Ignite 2019 conference.

In other words, Teams now generates a sharing link when users share files. The sharing link defines who can access the file and what level of access they have to the file (read-only or edit). Teams respects the SharePoint sharing policy for the organization, which dictates the range of sharing links that can be used in an Office 365 tenant. Settings for individual sites can downgrade sharing to a more restrictive level.

Sharing in a Channel

Sharing files in Teams differs between channel conversations and personal chats. When a team member uploads a file to a channel, all team members automatically have access to the file, which is stored in the folder for the channel in the team’s SharePoint document library. There’s usually no need to edit the permissions on a file shared within a channel. You can use a private channel if you want to restrict access to a specific subset of team members and upload the files to that channel.

Alternatively, you can apply a sensitivity label with encryption to confidential information to restrict access to people with the right to view the content. This is sometimes done to restrict access to specific information to the tenant members of a team where guest members are present. Remember that even though guests won’t be able to access the content of protected documents, they’ll be able to see document metadata such as titles.

Sharing in a Chat

When a chat participant uploads a file, the file is stored in the Microsoft Teams Chat Files folder in their OneDrive for Business account and view-only access is granted to the chat participants. People who join the chat later aren’t included in the sharing link and you need to add them to the list of people with permissions (Figure 1).

Sharing a file in a Teams chat
Figure 1: Sharing a file in a Teams chat

It’s easy to open the file in OneDrive for Business and amend its sharing permissions to add new chat participants (Figure 2).

Editing access for a shared file
Figure 2: Editing access for a shared file

However, if you know that multiple people will join a chat in the future and you want them to have access to the files shared in the chat, you can amend the sharing link before posting the file. In Figure 3 we see that the link chosen allows access to everyone in the tenant. This might be appropriate in some situations, but most commonly you’ll probably want to add specific people to the link, especially if some guest users or federated users in other tenants are included in the chat.

Editing the sharing link for a file in a Teams chat
Figure 3: Editing the sharing link for a file in a Teams chat

Sorry – No Access

When Teams uploads a file to a chat, it evaluates if the participants will be able to access the file in OneDrive for Business. It’s unlikely that you will see this when sharing files in chats with other tenant users, but it can happen when chatting with people in other Office 365 tenants. To solve the problem, click to file to edit the sharing link to ensure that the person has access before completing the upload (or adjust sharing in OneDrive for Business afterwards).

Teams detects that a chat participant won't be able to access a shared file
Figure 4: Teams detects that a chat participant won’t be able to access a shared file

Federated Sharing

I’ve also seen some reports that the attach file icon is not shown in some chats, usually those with federated users in other Office 365 tenants. If this happens, try opening the chat in a separate window as the icon seems to be available on a consistent basis there. Because Teams now uses the Office 365 sharing model, if you share a document in a chat with a federated user, Teams creates a new Azure AD guest account for that person, which is then used to access the document. A bug appears to stop the new guest account opening the document from Teams, but if they copy the link it will work in SharePoint Online. Chasing down bugs is common when new mechanisms are introduced, and I am sure that Microsoft will fix this problem soon.

Consistency Across Office 365

Support for sharing links inside Teams means that Office 365 now has a consistent approach to file sharing across its major apps. Like OWA, Teams adjusts the sharing model to meet its needs, but it’s still the same mechanism underneath.


Need to know more about how Office 365 sharing works? It’s all explained in chapter 8 of the Office 365 for IT Pros eBook.

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