Why is my Excel file XLSX?

How do I open XLS and XLSX files?

XLSX and XLS files are Microsoft Excel Spreadsheets commonly used to store financial data and to create mathematical models. 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.

There are differences in the XLSX and XLS formats created by Excel. While XLS files use a proprietary binary format, XLSX files use a newer file format referred to as Open XML. The XLS extension is used by Microsoft Excel 2003 and earlier and the XLSX extension is used by Microsoft Excel 2007 and later.

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File Viewer Lite is a free .XLSX and .XLS file opener that allows you to view Excel documents (including .XLSM files) in their native format without having to purchase and install Microsoft Excel. In addition to Microsoft Excel files, File Viewer Lite can open over 150 file types, including Microsoft Word documents, PDF files, images, video files, audio files, and more. You can also view unsupported proprietary document formats in the program's Text and Hex Views. These views display the contents of the document, which can provide useful information.

To view your XLSX or XLS files, download our free file viewer and drag and drop the .XLSX or .XLS file onto the program window. File Viewer Lite will open the file and display the document in its native format as if you were viewing the document with Microsoft Excel.

View all the features File Viewer Lite has to offer.

The file format of an Excel worksheet is .xlsx or .xls. Whenever the user opens any file, it is opened with the same extension. However, some users may encounter an error when trying to open or edit an Excel file in Office 2003, 2007, 2010, 2013, 2016, 2019, and 365. The error message displayed reads "Excel cannot open the file because the extension is not valid".

This article will provide you with comprehensive solutions to resolve the "Excel cannot open the file because the file format or file extension is not valid" error. You can change the file extension, use the Office repair utility, or use one of the best file repair software to repair Excel files. 

Excel Cannot Open The File Issue Overview

Sometimes, when you try to open or edit an Excel file in Microsoft Office 2003, 2007, 2010, 2013, 2016, 2019, or 365, you may encounter the following problem:

"Excel cannot open the file 'filename.xlsx' because the file format or file extension is not valid. Verify that the file has not been corrupted and that the file extension matches the format of the file."

It usually indicates the file is not compatible with the Excel version of the file that has come corrupt or damaged. Here, we will show you all the possible solutions, and you can try these until your issue is fixed. Before you follow the solutions, check if Excel is working normally.

Step 1. Press Windows+R keys, type excel.exe /safe,and click "OK". Loading Excel without templates and add-ins allows you to see if the program works as it should or if it is corrupted.

Step 2. If Excel opens normally, check for any add-ins that are causing problems in Excel. Disable the add-ins and click on the "OK" button. Then, restart Excel to check if the problem is fixed. If not, move on to the fixes below.

We have full solutions to help you solve Excel cannot open the file because the extension is not valid issue in this post. In the beginning, you can watch a video tutorial to troubleshoot. The key moments in this video are as follows:

• 00:26 Ensure you have enough permissions
• 01:03 Enable Safe Mode
• 01:26 Open Excel in Safe Mode
• 01:43 Repair and recover the Excel

How to Fix Excel Cannot Open the File Because the Extension Is Not Valid on Windows 10/8/7

There are three useful solutions in total here to solve the Excel cannot open file problem. 

Fix 1. Use EaseUS File Repair Tool

If the "Excel cannot open the file because the extension is not valid" problem is caused by file corruption and not by file compatibility, you need a professional file repair program to help you fix the problem. 

EaseUS Data Recovery Wizard is an all-in-one tool that can help recover deleted files and repair corrupt files easily and efficiently.

EaseUS Excel Data Recovery/Repair Tool

• Recover corrupted Excel files in XLSX/XLS formats
• Repair single or multiple Excel files without quantity limit
• Support MS Excel 2019, 2016, 2013, 2010, 2007, 2003, XP, 2000, 97, and 95 versions
• Support other document repairs like Word and PDF

Go ahead and download the EaseUS MS Office document repair tool, then follow the step-by-step guides below to repair damaged Excel files in three steps:

Step 1. Launch EaseUS Data Recovery Wizard, and then scan disk with corrupted documents. This software enables you to fix damaged Word, Excel, PPT, and PDF files in same steps. 

Step 2. EaseUS data recovery and repair tool will scan for all lost and corrupted files. You can find the target files by file type or type the file name in the search box. 

Step 3. EaseUS Data Recovery Wizard can repair your damaged documents automatically. After file preview, you can click "Recover" to save the repaired Word, Excel, and PDF document files to a safe location.

Fix 2. Change the Excel File Extension to Fix Excel Cannot Open the File

Many times, this error occurs due to the incompatible file extension of the Excel file. MS Excel saves Excel workbooks as XLSX or XLS files by default. Excel 2003 and earlier versions save files as XLS, whereas Excel 2007 and later versions like Excel 2010, Excel 2013, Excel 2016, and 2019 save files in XLSX file format. You can change the default file format for the corresponding Excel version to any other file format supported by MS Excel.

Step 1. Open Microsoft Excel and go to the "File" tab.

Step 2. Click "Export" and choose "Change File Type".

Step 3. Change the file extension to any other file format that MS Excel supports and click "Save As" (Excel not saving changes? Quick tips are here). Then, Check whether Excel can open your file or not. 

Fix 3. Open Excel File Using the Open and Repair Feature

The "Open and Repair" is a built-in easy-to-use MS Excel utility that allows you to correct the "Excel cannot open the file because the file format or file extension is not valid" error.

Step 1. Start Office Excel. On the File menu or the Microsoft Office button, click "Open".

Step 2. In the Open dialog box, click to select the inaccessible Excel file.

Step 3. Click the down arrow on the Open button, and then click "Open and Repair". Microsoft Office will then start to check the Excel document and repair problems or corruption it found. 

How to Fix Excel Cannot Open the File Because the File Format or File Extension Is Not Valid on Mac

Some users have reported that they couldn't open Excel files on Mac. They also receive this error - Excel cannot open the file because the file format or file extension is not valid. If you are faced with this error, you are unable to view or edit your Excel file. Follow the solutions below, and you can troubleshoot the Office problems.

Fix 1. Restart Excel on Mac

Step 1. Quit the Excel application: click "Excel > Quit Excel".

Step 2. Try to open your Excel file on Mac again.

Fix 2. Restart Mac

Go to the "Apple menu > restart".

Fix 3. Change Excel File Format on Mac

Step 1. Click "File" from the menu bar.

Step 2. In the "Export To" pop-out menu, pick "Excel".

Step 3. To adjust the file format between XLSX and XLS, click "Advanced Options" and choose the one you want.

How to Recover Excel File When the File Format or File Extension Is Not Valid

If your unsaved Excel file cannot be opened because the file format or file extension is not valid, how would you recover unsaved Excel files?  In this case, try the two ways below. 

1. Restore Unsaved Excel Wordbook from Previous Versions

This method only restores lost files to a previous version. It means that you might lose some changes you may have made to the document.

Step 1. Right-click the inaccessible Excel file and choose "Properties".

Step 2. Open the "Previous Version" tab to list all the previously stored versions of the Excel file.

Step 3. Choose the most recent version and click "Restore" to retrieve the spreadsheet.

2. Restore Unsaved Excel File Using AutoRecover

This method only works if you have turned on the AutoSave feature in Microsoft Excel. This feature is also helpful for recovering unsaved Word documents. 

Step 1. Open Office Excel and head into the "File" tab > click "Info".

Step 2. Besides Manage Versions, you'll see all autosaved versions of your file.

Step 3. Open the file in Excel and click "Restore". 

Step 4. Save the file with a new file name and set the extension as .xlsx.

Important Tips: How to Prevent Excel Files from Getting Loss

There are many ways to prevent data loss. If you have lost important Excel files due to accidental deletion, hard drive formatting, or virus attacks, you can use the EaseUS Data Recovery Wizard tool to retrieve lost data. Another crucial point to avoid data loss is backing up your Excel file on a regular basis.

1. Recover Deleted or Lost Excel Files with File Recovery Software

In addition to restoring unsaved Excel caused by Excel crashes when saving or other reasons, many users may want to recover lost excel spreadsheets caused by accidental deletion, OS crash, hard drive damage/corruption, or lost partition. In these cases, you have to resort to a professional file recovery tool for help. And, EaseUS file recovery software is worth trying. It allows you to recover deleted DOC/DOCX, XLS/XLSX, PPT/PPTX, PDF, CWK, HTML/HTM, INDD, EPS, etc. with a few clicks.

Give it a try to get your lost Excel back immediately:

Step 1. Select location and click "Scan"

Choose the drive or a specific folder on Desktop or somewhere else where you lost the excel files, and click the "Scan" button.

Step 2. Locate your excel files

To quickly find the Excel files from the scan results, click the "Documents" option in the left panel. Choose "Excel", and click "Preview" to check if the Excel files are the wanted ones.

Step 3. Recover Excel files

Finally, select the desired Excel files and click the "Recover" button. Then, select a folder to save the Excel files to another location.

2. Back Up Excel File Automatically

If you modify and change your worksheet frequently, turning on the AutoSave feature is a good idea. Or, you can manually copy and backup your file to another safe location in case of accident.

Final Words

"Excel cannot open the file '(filename)' .xlsx because the file format for file extension is not valid" is a normal error that you can face while opening an Excel file. With the help of the above methods, this error can easily be resolved without data loss.

If Excel cannot open the file problem is due to file corruption, the EaseUS file repair tool can help you fix and recover the Excel file with a few clicks pretty quickly. It is good at repairing photos, videos, documents, and other files on the hard drive, SD card, memory card, or any other storage medium. No matter whether they are lost or exist on your devices. It's worth a shot.

The following four frequently asked questions are extremely relevant to the "Excel cannot open the file because the file format or file extension is not valid" error. If you also have any of these problems, you can find the methods here.

1. How do I fix the file format or file extension is not valid?

You can try to fix the "Excel cannot open the file because the file format or file extension is not valid" error by changing the file extension:

Step 1. Open your Excel file. On the taskbar, select "File" and then choose "Options" > "Export" > "Change File Type".

Step 2. You can directly change the file extension depending on the version of Excel installed.  Click "Save As". Then, check if the error "Excel cannot open the file" is resolved or not.

2. How do I recover an Excel file format or file extension that is not valid?

You can restore the Excel file format, or the file extension is not valid from previous versions.

Select the damaged file. Right-click it and click "Properties" > "Previous Version". A list of previous versions will appear; you need to select the option you are interested in and click "Restore" to recover. Previous versions come from File History or restore points.

3. What does file extension not valid mean?

"Excel cannot open the file '(filename)' .xlsx because the file format for file extension is not valid" is a common error that many users may encounter while opening a .xlsx file, especially when opening a spreadsheet received through an email. The possible reasons for this issue might be:

• The Excel file is corrupt or damaged.
• The Excel file is not compatible with the version of MS Excel you're using.

4. Why can't I open an XLSX file?

When the Excel file is corrupted, not compatible with the Excel version, infected by the virus, or received by email, these are the common causes of the "Excel cannot open the file because the file format or file extension is not valid" problem. If any of these problems appear, you can't open your XLSX file. 

How do I convert XLSX to Excel?

How do I change my default XLSX?

How do you fix Excel Cannot open the file XLSX because the file format or file extension is not valid?

How do I change the file type in Excel?