"Too many columns" for SharePoint upload

SharePoint has a limitation on number of columns in a single document library or a list, so SharePoint Uploader will warn you if you try to go over that limit

When uploading archives to SharePoint using our Uploader on the 3rd step you have an option to select metadata fields from your archive that you want to transfer to SharePoint.

Click on "Review and map fields between Notes and SharePoint"

For each selected field the tool will create a column in the SharePoint library or list. However, SharePoint has limitations on the maximum number of columns that each library or list can have and the tool will warn you if you select too many columns.

Warning message "Too many columns selected"

In this situation, we recommend that you unselect metadata fields that you don't plan to use in SharePoint views or for search. That information will not be lost, it is still preserved inside your PDF documents that are uploaded to SharePoint.

If you disregard this message and start the upload without deselecting fields you will probably get this error and it will cause the upload to fail:

ERROR SharepointUploader.MetaData.MetaProcessor - Microsoft.SharePoint.Client.ServerException: The column cannot be added because the total size of the columns in this list exceeds the limit. Please delete some other columns first.

The limitation depends on the type of each column. Each type has its own size, and the total size of all columns in a library or a list must be under a limit. You can read the details and find the sizes of each column type in this article on Microsoft Docs.