What is the default file format for saving files in Excel 2019?

The default file format for saving files in Excel 2019 is .xlsx. This format, introduced with Excel 2007, is based on the Open XML format and provides several advantages over older formats, including better data management, increased support for larger file sizes, and improved data recovery capabilities.

The .xlsx format allows for the storage of complex data types and is optimized for collaboration and sharing. It supports features such as charts, formulas, and tables, making it suitable for a wide range of tasks in Excel. When users choose to save their work without specifying a different format, Excel automatically saves files in .xlsx to ensure that all features are preserved and to ensure compatibility with other versions of Excel that also utilize this format.

The other formats listed, while useful in certain contexts, do not serve as the default save option in Excel 2019. For instance, .xls is an older format used in previous versions of Excel, while .csv is primarily used for simple text-based data and does not support advanced Excel features like formatting or formulas. The .txt format is even more basic, storing plain text without any special data structures or formatting capabilities that Excel provides.