What is an XLS/XLSX file?

XLS/XLSX File (definition)

An XLS file is a spreadsheet file format used by Microsoft Excel versions 1997 to 2003. It is based on a proprietary binary format that supports features like data organisation, formulas, charts, and basic formatting.

An XLSX file is the newer spreadsheet format introduced with Microsoft Excel 2007 and is based on the Open XML standard. XLSX files offer improved data compression, larger file capacity, and better compatibility with other software compared to the older XLS format.

Both file types are widely used for storing, analysing, and sharing structured data, with XLSX now being the default format in modern versions of Excel. These files are compatible with many platforms, including QuickBooks Online (QBO), for tasks like importing or exporting financial data.