Uploading large Excel files to sharepoint online lead to corrupt excel files with CustomXML deleted

Hi kaibakker

There is a known issue with SharePoint Online that causes Excel files with large CustomXML attachments to become corrupted when they are uploaded. The issue is that SharePoint Online has a limit of 5MB for the size of a single attachment. If a CustomXML attachment exceeds this size, it will be deleted when the Excel file is uploaded. This will cause the Excel file to become corrupt and will prevent it from opening properly.

There is no workaround for this issue at this time. However, there are a few things you can do to prevent it from happening:

• Reduce the size of your CustomXML attachments. If possible, try to reduce the size of your CustomXML attachments so that they are no larger than 5MB. You can do this by removing unnecessary data from the attachments or by compressing them.
• Use a different file sharing service. If you need to share Excel files with large CustomXML attachments, you can use a different file sharing service that does not have a size limit for attachments. Some popular file sharing services that do not have size limits for attachments include Dropbox, Google Drive, and OneDrive.

I hope this helps!