On Your hint I found this:
https://answers.microsoft.com/en-us/msoffice/forum/msoffice_excel-mso_other-mso_2010/excel-fills-spreadsheet-with-blank-columns/4a726e7b-a4a6-40ba-8528-2946a3a39e85?auth=1Apparently Excel will sometimes fill the sheet with not really empty columns.
I tried the solution given above. There are two given.
The first is to select all the empty columns by:
- Click the header of the first blank column
Press Ctrl+Shift+right arrow which selects to XFD
Press Ctrl+Minus to remove everything.
This didn't work. From the explanation Excel deletes them but adds back in the full count of columns.
The second solution works:
- Click the header of the first blank column
Press Ctrl+Shift+right arrow which selects to XFD
Right Click on the Selected area and select Hide.
Save sheet.
Works great. Except it really doesn't solve the problem, it just hides it. If you inspect the colModel there are still 16,384 columns defined, they're just hidden. What a waste.
There must be some way to determine "end of sheet".
In Excel if you click Ctrl-End it properly goes to the correct lowest
right cell of the active sheet area. Somewhere they must keep track of that?
Active sheet area rather the whole skeleton.
So it looks like this is a common Microsoft Problem which doesn't bother them
but messes up your import.
Since getting people to do this Hide before using a website to display or import a sheet is impractical you really need a means to test for "empty" columns and trim them. For in house use I can trim them but a general open sheet import on the web such as your demo page will have problems.
Hope that helps.