Keep the 

Google Sheets:

  1. From the File menu, select Download as then select Tab-separated values (.tsv, current sheet). This will download the currently selected sheet as a tab-separated .TSV file, inheriting the name of your spreadsheet. Select the Save as… or Save File As… command from your browser's File menu.
  2. Name your file and specify the file type as a Text File (*.txt). Click Save.

Apple Numbers:

  1. From the File menu, select Export To… then select TSV. This will save the currently selected sheet as a tab-separated .TSV file, inheriting the name of your spreadsheet.
  2. Name your file and leave the settings as default (Text encoding UTF-8) specify the file type as a Text File (*.txt). Click Save.

Microsoft Excel:

  1. Open the File menu and select the Save as... command.
  2. In the Save as type drop-down box, select the Text (tab-delimited) (*.txt) option.
  3. Select the Save button. If any warning messages pop up, select the OK or Yes button.