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Starting with Excel 2007 Microsoft introduced a series of new file formats to replace the .xls. Each of these new formats has different functionality and uses. It is important to be familiar with the different formats, particularly if you regularly work with large documents. This technical update details the file extensions available in Excel and when AMT recommends that these should be used. You can see the difference between two of the most commonly used file formats by downloading the files below and observing how long they take to open.

 

These files do not contain real data. Please feel free to duplicate the data to increase the file size and see how it affects the file type’s load time.

 

 

File extension

File format

Description

When to use

.xlsx

Excel workbook

This is the main replacement for the former binary .xls format. For enhanced security, this format does not support Excel macros. Underlying this format is a ZIP archive of XML documents.

The default Excel format if macros are not used in your model.

.xlsm

Excel macro-enabled
workbook

Exactly the same as .xlsx, but with the ability to support Excel macros.

The default Excel format if macros are used in your model.

.xlsb

Excel binary workbook

An Excel macro-enabled workbook. The file information is stored in binary format rather than as XML documents.

This file format is approximately twice as fast as .xlsx at opening and saving Excel workbooks. This is particularly useful for very large files (greater than 10MB). This file extension cannot be used by non-Excel applications such as Bloomberg and Capital IQ, so if these systems access your Excel file, then this file format should not be used.

.xltx

Excel template

A template Excel workbook.

This format should be used if a standard Excel file is to be used as a starting point for other Excel workbooks.

.xltm

Excel macro-enabled
template

A template Excel workbook
with macro support.

This format should be used if a standard Excel file is to be used as a starting point for other Excel workbooks and contains macros.

 

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