Files with .xlt extension are template files created with Microsoft Excel which is a spreadsheet application which comes as part of Microsoft Office suite. Microsoft Office 97-2003 supported creating new XLT files as well as opening these. The latest version of Excel is still capable of opening this old format template files. Such a template file is used to quickly create new Excel files with default data and settings such as page formatting, font size, margins, charts, etc which can be further saved as new .xls files.
XLT File Format
The XLT file format is based on Excel binary file format that initially came supported with Excel 97-2003 version. It was replaced with XLTX file format with the introduction of Excel 2007 which is based on Office Open XML format. Other than Microsoft Excel, there are other applications that support working with this file format such as Lotus Translation Table, PlanMaker, LibreOffice Calc, etc. Several applications and APIs are available to convert XLT to other file formats such as: