Convert EXCEL to XLSX online for free
1: Choose multiple local EXCEL files or enter the URL of an online EXCEL file. 2: Choose "XLSX" as target format and set options. 3: Click the "START CONVERSION" button to convert EXCEL files to XLSX online.
Choose filesChoose files or enter remote file URLenter remote file URL
Set conversion options (optional)
Microsoft Excel Binary File Format
File extension: .xls
Microsoft Excel up until 2007 version used a proprietary binary file format called Excel Binary File Format (.XLS) as its primary format. Excel 2007 uses Office Open XML as its primary file format, an XML-based format that followed after a previous XML-based format called "XML Spreadsheet".
Office Open XML Document
File extension: .xlsx, .xlsm
The Office Open XML file formats are a set of file formats that can be used to represent electronic office documents. There are formats for word processing documents, spreadsheets and presentations as well as specific formats for material such as mathematical formulae, graphics, bibliographies etc.