Update Square from a supplier CSV

The safest way to change an existing Square catalog is to edit your own export and send it back. Square matches items on the Token column, so that column has to survive the round trip untouched. No column may be reordered or deleted. Hand editing an export in a spreadsheet breaks one of those rules sooner or later. Drop your Square export and the supplier file together on this page. Products are matched by SKU, then GTIN, then name, and the output is your export with only the approved cells changed. Every other cell, column and header is copied exactly as Square wrote it. Products the supplier no longer lists are reported and left alone.