MS Excel - Excel File Formats Explained

Excel supports multiple file formats, each designed for different purposes such as compatibility, speed, security, or storage efficiency. Choosing the correct format ensures that features like formulas, formatting, and macros behave properly when the workbook is opened in different environments or shared with others. Understanding these formats avoids errors and helps maintain the integrity of your data.

XLSX – The Standard Workbook Format

XLSX is the default Excel file type for most users. It supports formulas, charts, conditional formatting, data validation, and large sheets while compressing data efficiently. Because it is based on XML, it is stable, widely compatible, and suitable for everyday work ranging from simple lists to advanced reports.

XLS – Older Legacy Format

XLS was the standard before 2007 and remains recognized for compatibility with very old versions of Excel. However, it limits storage capacity, lacks newer features, and can cause formatting issues when opened in modern Excel. It should be used only when working with legacy systems that cannot handle newer formats.

XLSM – Macro-Enabled Workbooks

XLSM files allow VBA macros to run and store user-developed automation. Regular XLSX files strip out macros for safety reasons, so any workbook containing buttons, coded functions, or automation should be saved as XLSM. This format is important for reusable workflows, dashboards, or automated reports.

CSV, PDF, and Specialized Formats

CSV stores values in plain text, making it perfect for sharing data with databases, web apps, or scripts that do not read Excel formatting. PDF creates a locked visual copy for viewing or printing but cannot be edited easily. Other formats like XLTX (template), XLTM (macro-enabled template), and XML spreadsheets support advanced workflows when flexibility or structure is important.