Start Free Course

Excel Extensions

Written by ExcelMojo Editorial Team ExcelMojo Editorial Team ExcelMojo editorial profile and article credentials. Full Bio
Reviewed by Dheeraj Vaidya, CFA, FRM Dheeraj Vaidya, CFA, FRM Reviewed for accuracy, clarity, and editorial standards. Full Bio
Updated Apr 23, 2026
Read Time 9 min

What Are Extensions In Excel?

Excel Extensions in files are the secondary filenames added at the end of any filename to identify the application type such as .doc, .docx, .xls, .xlsx, .ppt, .pptx, .html, .gif, etc. These are three to four letters long, and attached to the primary filename. Extensions indicate the Excel file type and the format of the data it contains. They help users choose which application to open and run the specific file correctly.

For example, the below image shows an Excel worksheet containing employee appraisal and promotion eligibility details.

📥Download the ready-to-use Excel template to practice this tutorial yourself.

Download Excel Template

Frequently Asked Questions (FAQs)

1. Which Excel extension should I use?

We should use the Excel extension in the Save as type: field of the Save As window that best suits our file format and data type. The below image highlights the Extensions we can typically use to save our Excel files.

• If our Excel file does not contain macros, use the XLSX extension.
• If our Excel file contains macros, use the XLSM extension.
• If we want to reduce our Excel file size, use the XLSB extension.
• If our Excel version is older than 2007, use the XLS extension.
• If our Excel file contains Excel add-ins, use the XLAM extension.

Excel Extension - FAQ

2. What is difference between XLS and XLSX Excel Extensions?

The difference between XLS and XLSX are:

• The XLS file format arranges data as binary streams, while the XLSX extension uses the XML file format to store the data in a compressed XML file in ZIP format.
• The number of rows and columns in an XLS file is fewer than that in an XLSX file, but the XLS file size is comparatively larger than an XLSX file size.

3. What is the smallest Excel extension file type?

The smallest Excel extension file type we can use if our file is over 10 MB is XLSB. Otherwise, it is best to stick to XLSX or XLSM file formats.

Download Template

📥Download the ready-to-use Excel template to practice this tutorial yourself.

Download Excel Template

This has been a guide to Excel Extensions. Here we use the steps to save the files in the top five excel file formats or extensions & a downloadable template. You can learn more from the following articles –