10 Difference Between XLS And XLSX

XLS (Excel Spreadsheet) and XLSX (Excel Open XML Spreadsheet) are both file formats used to store and manage data or create mathematical models in Microsoft Excel. These files store data in worksheets that contain cells arranged as a grid of rows and columns. Excel spreadsheets may also contain charts, mathematical functions and various kinds of cell formatting.

Spreadsheets are often used in business contexts to store financial data and to perform mathematical computations. Let us talk in more details about the XLSX and XLS Microsoft files, their capability, and other related details.

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What Is XLS?

XLS stands for Excel spreadsheet. In other words, an XLS file is a spreadsheet file created by Microsoft Excel or exported by another spreadsheet program, such as OpenOffice Calc or Apple Numbers. It contains one or more worksheets, which store and display data in a table format. XLS files may also store mathematical functions, charts, styles, and formatting.

Microsoft Excel files use a proprietary format for storing Microsoft Excel documents. This file format is known as the Binary Interchange File Format (BIFF).

The Microsoft Excel Spreadsheet (XLS) binary format was introduced in 1987 with the release of Excel. XLS files became one of the most common file types for saving spreadsheets until the release of Excel 2007. With this release, Microsoft introduced the Microsoft Excel Open XML Spreadsheet (XLSX) format and replaced XLS files with .XLSX files as the standard file for saving spreadsheets in Excel.

You may encounter XLS files in home, school, and business environments when organizing, analyzing, manipulating, or visualizing data. Each worksheet included within a spreadsheet consists of a table with rows and columns and the cells in a table may contain manually-entered data or the results computed from the data of other cells.

Also Read: Difference Between File And Folder

What Is XLSX?

XLSX is a Microsoft Excel spreadsheet developed by Microsoft for Windows, MacOS, Android and iOS. It features calculation, graphing tools, pivot tables and a macro programming language known as Visual Basic for Applications.

In Office 2007, Microsoft added the “x” to the end of many of the office file extensions. “doc”, “ppt”, and “xls”, became “docx”, “pptx”, and “xlsx”.

The new file formats contain a folder structure, with small files covering every detail. This folder structure is then compacted in a .zip archive and given a four letter file extension like .xlsx. If you rename the file and change the file extension to .zip, you can reverse the process and see the inner details of the file.

For Excel, there are two major differences:

  1. The “x” version of the file zips the data. So, whenever you open an “xlsx” file, Excel is first unzipping the data, and then opening file.
  2. “xls” was a binary data format, and “xlsx” is an XML data format. To the normal end user, there is really no difference on this point.

XLSX is mainly for Excel operations, much beyond plain data. You have formulas, formats, pivot tables, charts, and VBA code in it. It’s not designed as a common data format for further data manipulation outside of Excel, although other tools can read plain data from it. 

XLS VS XLSX: Key Difference

File Format

  • The XLS format is the older binary file format used by earlier versions of Microsoft Excel (up to Excel 2003).
  • The XLSX format is the newer XML-based file format introduced with Excel 2007 and later versions.

File Size

  • XLS files tend to be larger in size compared to XLSX files due to their binary nature.
  • XLSX files are generally smaller in size because they are compressed XML-based files.


  • XLS files may not be compatible with newer versions of Excel or other spreadsheet software without conversion.
  • XLSX files are more widely compatible across different versions of Excel and other spreadsheet software.

Data Integrity

  • XLS files can sometimes be more susceptible to data corruption or loss due to their binary format.
  • XLSX files have improved data integrity due to their XML-based format and compression.

Features and Formatting

  • XLS format may not support some of the advanced formatting features introduced in later versions of Excel.
  • XLSX format supports a wider range of advanced formatting features and enhancements.

File Extension

  • XLS files have the “.xls” file extension.
  • XLSX files have the “.xlsx” file extension.

File Structure

  • XLS files use a binary file structure that can make them harder to parse and manipulate programmatically.
  • XLSX files use a ZIP archive containing XML files, making them more accessible for programmatic manipulation.

Compatibility Mode

  • Newer versions of Excel can open XLS files, but they might be opened in compatibility mode, which can limit certain features.
  • XLSX files are natively supported by newer versions of Excel, allowing access to all features.

Macros and Security

  • Macros in XLS files have security concerns and are often disabled by default due to the risk of viruses and malicious code.
  • Macros in XLSX files can be better managed and controlled, enhancing security.

Metadata and Recovery

  • XLS files might have limited metadata and recovery options in case of file corruption.
  • XLSX files include more comprehensive metadata and improved recovery options.

Also Read: Difference Between Rows And Columns In Excel

XLS  vs XLSX: Key Takeaways

Basis of Comparison XLS XLSX
Version XLS is the older version of Microsoft Excel. XLSX  is the latest version of Microsoft  Excel
Main Difference XLS is the default file format for the 2003 version of Excel XLSX is the file format for versions since 2007.  
Storage of Information XLS is based on BIFF (Binary Interchange File Format) and as such, information is directly stored to a binary format. XLSX is based on the Office Open XML format, a file format that was derived from XML. The information in an XLSX file is stored in a text file that uses XML to define all its parameters.  
Speed performance XLS version of the file is faster especially on files that require the use of complex formula for a large set of data.   XLSX version of the file is slower especially on files that require use of complex formula for a large set of data.
Readability XLS is readable by all Microsoft Excel versions.  XLSX is only readable by Microsoft Excel versions 2007 and onwards.  
Capability XLS is capable of holding the spreadsheets either containing Macros or not. XLSX is not capable to support Macros.  
Based On XLS is a proprietary binary format. XLSX is based on office open XML format.  

Also Read: Difference Between Single And Multiple Document Interface