Why does sending large attachments (>3MB) with MS Graph API just works without upload session?

Hi @Frederik Gysel

The documentation you referenced is correct in stating that for files under 3 MB, you can use a single POST request, and for files between 3 MB and 150 MB, you should create an upload session and use PUT requests to upload the file in chunks.

However, if you were able to upload a 10 MB file using a single POST request, it might be due to specific configurations or updates in the API that allow for larger file uploads in certain scenarios. It's also possible that the API has some flexibility or that there are exceptions not explicitly mentioned in the documentation.

To ensure consistent behavior and avoid potential issues, it's generally best to follow the recommended approach in the documentation. If you continue to experience discrepancies, you might want to check for any recent updates or changes in the API documentation or reach out to Microsoft support for clarification.

Hope this helps.

If the reply is helpful, please click Accept Answer and kindly upvote it. If you have additional questions about this answer, please click Comment.