What type of file is an excel file

Probably 99% of all Excel workbooks are saved in the XLSX file type these days. But there are various other file extensions available: For example XLSM, XLSB or “older” Excel users might still remember the XLS file type. What are the differences of these file types? And even more important: Which one should you use?

When you save an Excel workbook for the first time or use the “Save As” function, you are asked for a folder, file name as well as the file type. By default, Excel suggests the XLSX file type (unless your file has VBA macros). The window looks similar to the screenshot on the right side.

So which file type are you going to use? The answer – like so often: It depends. Before we conclude in a decision tree, we we take a look at the most important file extensions in Excel with their advantages and disadvantages first.

XLSX

The “default” file extension is XLSX. The large majority of Excel workbooks uses this format these days. Microsoft says in the Excel help text about the XLSX file format:

The default XML-based file format for Excel 2007-2013. Cannot store Microsoft Visual Basic for Applications (VBA) macro code […].

Most of the time you use the XLSX format: It’s save (can’t store malicious code), has the maximum number of rows and columns and is best known. XLSX is available since Excel 2007 and replaces the old XLS file type. It uses the open XML standard so which is documented well.

Knowing these quick facts, there are the following advantages and disadvantages for the XLSX file format:

Advantages	Disadvantages
The default file format and because of that the best known and widest spread file type. Can use up to 2^20 (1048576) rows and 2^14 (=16384) columns. Uses the open file format and is in general accessible with other applications. Secure because it can’t save VBA macros. Can use and save all the functions available in Excel.	A little bit contradicting: But not being able to include VBA macros can be an advantage and disadvantage at the same time. Needs more disk space than other file formats (e.g. XLSB). Can’t be opened with Excel versions before 2003 (e.g. 2003, at least without any further conversion of Excel extension/ add-in).

XLS

The XLS file type has been the default Excel file extension and format before Excel 2007. In Excel 2007, XLSX replaced the XLS format. Therefore, XLS is kind of outdated right now. In the daily life you won’t find it often any more. But some data base tools still export data as XLS files.

The XLS file type has some disadvantages towards the newer file types XLSX or XLSM: It’s rather unsafe as it can contain VBA macros with malicious code. Also, it needs more disk space than the other file types and at the same time has less rows and columns.

On the other side the only advantage: You can easily open XLS files with older versions of Excel.

Advantages	Disadvantages
Can be opened with Excel versions before 2007 (e.g. 2003).	Unsafe as it can contain VBA macros. Needs more disk space than most of the other file formats (e.g. XLSX, XLSB). Can’t use all newer Excel functions, e.g. formulas or functionality (you will be warned when saving an XLS file though). Can only use up to 65,536 (2^16) rows and 256 (2^8) rows. Outdated…

XLSM

If you include VBA macros in your XLSX file, you will be asked to change the file extension to XLSM. Only that way you can save your macro within the Excel file (there are other file types possible, e.g. XLSB – but you can’t use XLSX for VBA macros). Therefore, it has most of the advantages and disadvantages of the XLSX file type. Positive: You can immediately identify Excel files with VBA macros.

Advantages	Disadvantages
The default Excel file type for workbooks with VBA macros. Can use up to 2^20 (1048576) rows and 2^14 (=16384) columns. Uses the open file format and is therefore accessible with other applications. Can use and save all the functions available in Excel. Uses the open XML standard.	Unsafe: Can contain malicious code within the VBA part. Needs more disk space than other file formats (e.g. XLSB). Can’t be opened with Excel versions before 2003 (e.g. 2003, at least without any further conversion of Excel extension/ add-in).

XLSB

Many people don’t know that there is an actual alternative to the XLSX and XLSM file type: The XLSB file extension. XLSB files store the data a little bit different than the XLSX or XLSM file types: They don’t use the XLM file structure. Instead, XLSB files try to save disk space because the data is stored in the binary structure. The main difference: Binary files are computer- but not human-readable. For more information on binary files in general, please refer to this Wikipedia entry.

The main disadvantage: Binary Excel files can contain VBA macros. So unless you don’t know the origin of a file, please consider well before opening them. Besides that: All the other disadvantages seem minor.

Advantages	Disadvantages
Smaller file size. Faster opening and closing of files. Formulas with more than 8192 characters allowed. Can use and save all the functions available in Excel.	Security: Files can contain VBA code whereas XLSX files can’t. You can’t change the Excel ribbon. Some third party tools (e.g. OpenOffice) might not be able to open your file. You can’t open your files with Excel 2003 or earlier (which nowadays should not be a problem any more…). Not very well known. So people might get confused receiving XLSB files from you.

CSV

CSV stands for comma separated values. These files are basically plain text – so there are no formulas or formatting. CSV is often used for data exchange. Excel provides the functionality to import or even directly open CSV files.

The basic application for CSV files: Import or export data. Data base programs often export data as CSV files. Also if you want to transport Excel data into a database program, often the CSV file type works.

Advantages	Disadvantages
Smaller file size. Faster opening and closing of files. Unlimited rows and columns. No code or macros possible and therefore save to open.	CSV files are basically text documents and therefore can’t contain formulas or formatting, pure data. No more than one “worksheet”.

ODS

ODS stands for Open Document Spreadsheet. The file type is designed to work on both Excel and other applications, e.g. LibreOffice. From the Excel point of view, ODS doesn’t support all the features. Text and data is usually saved well though. But formatting and many other features (for example charts, tables, conditional formatting) might run into problems.

Advantages	Disadvantages
Can be opened in Excel and LibreOffice.	You might lose formatting or features which are not supported. For a detailed lists of the features supported, please refer to this website.

XLSX (Strict)

Besides the regular XLSX format, Excel offers to save your Excel workbook as “Strict Open XML Spreadsheet”. So what is the difference between those two? Basically, the two file types use the same structure. But:

The Strict variant has less support for backwards compatibility when converting documents from older formats.

Furthermore:

The Strict variant of XLSX disallows a variety of elements and attributes that are permitted in the more common Transitional variant […]

Advantages	Disadvantages
Same as XLSX. Additionally: Opening in other applications than Excel might work better.	Some backward compatibility problems might occur.

PDF

As you’ve probably heard of PDF files, we won’t go much into detail here. PDF stands for portable document format and has the reputation of not easily being manipulated. Also, it’s quite save to say that how a PDF file looks on your computer, it will most probably look like this on most other computers.

And that’s it for the advantages. I recommend using it when you present your final results in the following cases:

• The recipient of your file should not edit it any more.
• Formatting should be exactly preserved.
• There is no database included, just the summarized results.

That could be the case if somebody wants to check your results on an iPad or a similar device. But: In many cases it would be professional (and nice) to also send at least parts of your Excel file. That way, your recipient could at least take a look at the calculation process.

Advantages	Disadvantages
Static, therefore contents can not (easily) be manipulated. The document always look the same. No macros.	Formulas etc. will be lost. Difficult (and troublesome) to further edit the file. (Depending on the contents) large file size.

XLAM

XLAM is the file extension for Excel add-ins. Also our add-ins (for example the popular “Professor Excel Tools“) are XLAM files. They can contain VBA macros, worksheets as well as forms, images and individual ribbons. If you double click on such file, it will open in Excel and you can use the funcationality of the add-in. But next time you open Excel again, it won’t be available any longer. You rather have to enable the add-in within the options (File –> Options –> Add-Ins).

As the XLAM file type is not really an alternative for all the other file extensions above, we skip the advantages and disadvantages.

Comparison of file types

So if we put all the advantages, disadvantages and facts from above together, we come to the following comparison:

Which file type should you use?

Decision Tree

In order to define the best file type for your Excel workbook, please follow the decision tree.

• The first question: Do you just want to display your results only? Then you could also consider the PDF format. But if the recipient of your work wants to edit or follow up your calculations, you shouldn’t use PDF.
• Does your file contain VBA macros?
  • If yes, choose XLSB if you have a large file. Choose XLSM for a file size smaller than app. 10 MB.
  • If no and you got a large file (larger than app. 10 MB), also choose XLSB.
  • If no (you don’t have macros) and your file small, follow the tree on the right hand side.
• The lower two levels of the decision tree are just about compatibility: If you want to open and edit your workbook with another software, choose the strict XLSX or ODF format.
• If you want to make sure that you can open it with versions of Excel 2003 or earlier, go for XLS.

Summary

In conclusion, you can distill a quite short table (if you don’t need to consider old file types and other applications as LibreOffice). You just have to answer two questions: Do you need VBA macros and do you work with a large amount of data?

In this article, we’ll learn what are Excel file formats and extensions, and what distinguishes one from another. We’ll also see how to know the type of an Excel file and how to change it to another format when needed.

Excel has many different file formats or types that are distinguished by their extensions, and each file type has its purpose that makes it more useful for some tasks and situations than for others.

In the following table, I have listed the Excel file formats and extensions, along with a description of their purpose and characteristics.

Format/Type	Extension	Description and Purpose
Excel workbook (versions 2007 and later)	.xlsx	– Default Excel file for Excel 2007 and newer, based on the Office Open XML format. – Cannot store VBA macro code (to do that, you’ll need to use the dedicated format .xlsm).
Excel 97-2003 workbook	.xls	– Default Excel file for Excel 2003 and earlier, based on the Microsoft Binary Interchange File Format (BIFF8). – Unlike the .xlsx format, this file type can store VBA macro code.
Excel macro-enabled workbook (versions 2007 and later)	.xlsm	Excel workbook with macros for versions 2007 and newer (stores VBA macro code).
Excel macro-enabled workbook (2003 and earlier)	.xlm	Excel workbook with macros for versions 2003 and earlier (stores VBA macro code).
Excel binary workbook (versions 2007 and later)	.xlsb	– Default Excel binary workbook that uses the Microsoft Binary Interchange File Format (BIFF12) in Excel 2007 and newer. – Faster than .xlsx format – Can contain macros.
Excel template (versions 2007 and later)	.xltx	– Excel template for versions 2007 and newer. – A template is used as a strating point for creating new workbooks that will have the same layout, formatting, graphics, formulas, etc, without the need to recreate these aspects each time. – Cannot contain macros.
Excel template (versions 2003 and earlier)	.xlt	– Excel template for versions 2003 and earlier. – A template is used as a strating point to create new workbooks without the need to recreate each time the same layout, formatting, graphics, formulas, etc. – Can contain macros.
Excel macro-enabled template (versions 2007 and later)	.xltm	– Excel template with macros for versions 2007 and newer. – Unlike the .xltx, this template format stores VBA macro code.
Excel add-in (versions 2007 and later)	.xlam	Excel add-in with macros for versions 2007 and newer (stores VBA macro code).
Excel add-in (versions 2003 and earlier)	.xla	Excel add-in with macros for versions 2003 and earlier.

Now that we know the main Excel file formats and their extensions, let’s see how you could know which format is your Excel file and which extension it has, as well as how to change this format and extension (or if you want, how to convert an Excel file from one format to another).

B/ How to know the Excel file format and extension

If you don’t have the extensions displayed for your files in Windows, you still can know which format and extension they have.

To know the format of an Excel file and the extension:

• Right-click on the name of the Excel file.
• At the bottom of the list, click on “Properties”.
• “Properties” window opens in its “General” tab.
• “File Type” section shows the type and extension.

C/ How to change Excel file format and extension

You would need to change the type of an Excel file:

• If you’re using it for an app that requires a different type.
• or if you want to benefit from a characteristic that the current type doesn’t have and that is present in another type; for example, the support of macros (from xlsx to xlsm), or less weight (from xls to xlsx), or more speed (from xlsx to xlsb)…

To change your Excel file type/format (and extension):

• Click on File tab (Office button in Excel 2007).
• Click on “Save As”.
• Choose where you want to save your file.
• The “Save As” dialog box displays.
• Click on the drop-down “Save as type”.
• Choose the file format and extension you want.
• Finally, click on “Save”.
• The file has now the new format and extension.

Note that you can change your Excel file format and extension in Windows directly from the name file, by changing the extension while renaming it, if you have allowed the display of the file extensions in your system.

In the following, I will show you how to display the file name extensions in Windows 7, 10, and 11.

– Display the file name extensions in Windows 7

• Open any folder.
• In the top blue bar, click on “Organize”.
• Then, click on “Folder and search options”.
• The “Folder Options” dialog box displays.
• Click on the “View” tab of this dialog box.
• Go to the “Advanced Settings” section.
• Uncheck “Hide extensions for known file types”.
• Click “OK”.

– Display the file name extensions in Windows 10

• In any folder, click on the “View” tab.
• Check “File name extensions” checkbox.

You can also use the “Folder Options” dialog box to show the file name extensions in Windows 10, but I preferred to show you the fastest and easiest method.

– Display the file name extensions in Windows 11

• Open any folder.
• Click on the three dots … of the menu bar.
• Click on “Options”.
• The “Folder Options” dialog box displays.
• Click on the “View” tab of this dialog box.
• Go to the “Advanced Settings” section.
• Uncheck “Hide extensions for known file types”.
• Click “OK”.

D/ Wrap up

So, that was the article about Excel file formats, where I gave you a list of the main Excel files, along with their extensions and a description of their purpose. I also showed you how to know which type is your Excel file and what extension it has, as well as how to change the format (and extension) of an Excel file and when you’ll need to do it.

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