Photos not uploading correctly / no preview available

In the Teams desktop or mobile app, image and file previews are generated by the client. When the client cannot render a preview, it shows a generic broken-image icon, while the same content can still be viewed correctly in the web version.

From the documented behavior for Teams file and picture attachments:

• When attaching a file or picture in Teams, the app normally generates an inline preview for images, videos, and many document types.
• A preview will not appear if:
  • The user does not have permission to the file, or
  • The file is encrypted with certain sensitivity labels, or
  • The chat is with external users, or
  • The file type is not supported for preview (for example, .zip files).

In the web client, these same files can still be opened directly from the message, which is why they appear correctly there even when the native app cannot render the thumbnail.

Given that:

• The images are visible and open correctly in the web version.
• The desktop/mobile app shows only a broken-image placeholder.

The most likely causes are:

1. A temporary issue or bug in the current Teams client build affecting image preview rendering.
2. A permissions or sensitivity-label condition that prevents the native client from generating previews, even though the files themselves remain accessible.

To work around and validate:

1. Confirm that the images are standard supported formats (for example, JPEG or PNG) and not inside unsupported containers such as .zip files.
2. Open the affected messages in the web client and verify that the files themselves open correctly from there.
3. In the Teams app, try signing out and back in, or reinstalling/updating the client, to pick up any fixes to preview behavior.
4. If the chat involves external users or files stored in locations with strict sensitivity labels, test by sending a simple JPEG from a standard Teams channel or chat within the same tenant to see if previews work there.

If previews work in some chats but not others, the difference is likely due to file permissions or external-user conditions. If previews fail everywhere only in the app but always work on the web, it indicates a client-side issue that should be escalated to support with screenshots and client version details.

References:

• Send a file, picture, or link in Microsoft Teams