The 123 file type is a spreadsheet file that is associated with ‘1-2-3’ by IBM. It used to be a Lotus product until the company was purchased by IBM. Before the purchase, Lotus 1-2-3 used to be a very popular spreadsheet software application in the 80’s, until Excel emerged to take its place.

Mime type: application/vnd.lotus-1-2-3, application/x-lotus123, zz-application/zz-winassoc-123

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