.XLTHTML File Extension
File TypeMicrosoft Excel HTML Spreadsheet Template
File format categories include Binary, Text, XML, and Zip. The format of this file type has not been determined.
What is an XLTHTML file?
HTML version of a .XLT spreadsheet template created with Microsoft Excel, a spreadsheet application; contains HTML that renders the template using similar formatting as the original XLT file; used for viewing published spreadsheet information in a Web browser.
XLTHTML files were not popular and are no longer supported by Microsoft Excel. To publish a spreadsheet template for a Web browser, save the template using the .MHTML extension from the in Excel 2010.