Microsoft is changing how file uploads interact with Teams messaging.
Previously, users were blocked from sending Teams messages while a file upload was in progress, which interrupted real-time collaboration. With this update, file uploads run asynchronously in the background, so the message input box stays available throughout the upload.
This update affects all users who send files in Teams chats or channels, across Windows, Mac, Web, and Mobile.
Timeline
The rollout should be completed in August 2026.
How does this affect your users?
Previously, starting a file upload locked the message compose box until the upload finished. The user saw a message about the upload process. The screenshot below is from the end of June.
After this update, users can continue typing and sending messages while a file uploads in the background. The upload itself is unaffected, as files are stored and shared exactly as before.
Asynchronous file upload uploads the file in the background instead of blocking the compose box. Users can send new messages while a file is still uploading.
Nevertheless, users should not close the Teams client, as the upload requires a running client. Users will see the upload is in progress and in a “Sending” state. The message will be sent once the upload is completed. Users should also keep in mind that a message with a large attachment may arrive later than messages without one, particularly when the timing matters for context.
If the Teams client is closed, Teams does not continue the upload once the client is started again. The message remains in an ongoing upload state, without any progress. The message is just blocked and cannot be edited or deleted. Users have to resend the message.
