What is xlsm vs xlsx

Overview

XLSM and XLSX are virtually identical file formats that both use the modern XML-based architecture introduced in Excel 2007. The critical distinction lies in macro support: XLSM (Excel Macro-Enabled Workbook) can contain and execute VBA macros, while XLSX (Excel Spreadsheet) cannot. This single difference has significant implications for security, file sharing, and functionality that users should understand when choosing between formats.

Understanding Macros

Macros are sequences of automated actions recorded and executed within Excel. They allow users to automate repetitive tasks, perform complex calculations, and create custom functions. VBA (Visual Basic for Applications) is the programming language Excel uses for macro creation. Macros can significantly enhance productivity for power users and developers, automating workflows that would otherwise require manual data entry and manipulation. However, because macros are executable code, they present security risks if files come from untrusted sources.

XLSM Files - Macro-Enabled Functionality

XLSM files are designed specifically for spreadsheets containing VBA macros. When you save an Excel file with macros in XLSM format, the file preserves all macro code. Users opening an XLSM file will see a security prompt asking whether to enable or disable macros, giving them control over whether automated code executes. XLSM is essential for organizations and power users who rely on automated workflows, custom business logic, and complex calculations that extend Excel's native capabilities. Financial analysts, data engineers, and business operations teams frequently use XLSM files.

XLSX Files - Standard Format Without Macros

XLSX files are the universal standard for general spreadsheet use. They support all spreadsheet features including formulas, charts, pivot tables, formatting, and data validation, but cannot contain executable code. XLSX is the default format when saving in modern Excel versions. If you attempt to save a file containing macros as XLSX, Excel will warn you that macros will be lost. XLSX files are safer for sharing across organizations, particularly with external partners or untrusted sources, since no malicious code can execute.

Security Implications

The inability of XLSX to execute macros makes it the safer choice for file sharing. Malicious actors sometimes distribute infected Excel files with harmful macros that can compromise computer systems. XLSX files eliminate this attack vector entirely. However, this security benefit comes with a cost: legitimate macro functionality is disabled. Organizations must balance convenience against security when deciding whether to use XLSM. Best practices include only enabling macros for files from trusted sources and regularly scanning files with antivirus software.

When to Use Each Format

Use XLSM when you have intentionally created macros that enhance your spreadsheet's functionality and when you're working in a controlled environment. Use XLSX for all other purposes, especially when sharing files externally or with colleagues in different departments. If your spreadsheet doesn't require macros, always save as XLSX. Some organizations and security policies strictly prohibit XLSM files to enforce security standards. Cloud-based alternatives like Google Sheets further reduce the need for macro-enabled files through native automation features.