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Despite the increasing challenges from competitors like Google Sheets, Microsoft Excel remains the most used spreadsheet app. It’s the app of choice in most workplace settings. What’s more, it includes numerous tools that help streamline and ease workflows.

Excel, like every other Microsoft app, occasionally runs into issues. Most of these are mere annoyances and can be solved with one or two program or system reboots. However, the “Excel cannot open the file because the file format or extension is not valid” issue has proved to be more bothersome for several users.

If you encounter this message when you try to open a file in Excel (or an Excel file), this guide will be helpful. We explain the possible reasons why the error can occur and three solutions that could work for you.

Excel Cannot Open the File Because the File Format or File Extension Is not Valid

When any user encounters this error in Excel, it’s usually due to one of two reasons:

  • The file is corrupted.
  • The file extension isn’t supported.

A corrupted file is unlikely to be opened by the parent program. Even if it successfully opens, it’s likely to have multiple errors such as missing data or unreadable portions. Excel and several other programs go the extra mile and simply don’t open corrupted files. It’s up to the user to try and fix the file corruption first or use another document with uncorrupted data.

Sometimes, the corruption is caused by malware that infiltrated the system. This can happen if your system isn’t fully protected when working with Spreadsheets on the web. Unrelated internet activity can cause this as well. After all, some malware types are known to be distributed as macros that can attach to Office documents.

It is better to be prepared for anything. Auslogics Anti-Malware will protect you against online and offline threats, as your main or supplementary antivirus. It’s unobtrusive, lightweight, fast, and frequently updated.

Sometimes, this error could be due to incompatible or unsupported file formats. Versions of Excel since 2007 use Office Open XML as the primary file format but are backward-compatible with the earlier versions of Excel files. A glance at the file extension will tell you straight away whether the program can open that file.

If the file you’re attempting to open is in one of these formats, it won’t open because it’s been corrupted. That’s because the file extension is compatible with Excel:

Excel Workbook. xlsx

Excel Macro-enabled Workbook. xlsm

Excel Binary Workbook. xlsb

Excel Macro-enabled Template. xltm

Excel Add-in. xlam

Spreadsheet. xls

Excel Template. xlt

Excel Macro. xlm

In addition, documents in these non-Excel file extensions can be opened by the program, though functionality might be reduced in some fashion:

XML. Spreadsheet 2003 or XML formatted files. xml

Lotus Spreadsheets. prn

Tab delimited/Unicode text files. txt

Comma-separated values files. csv

Data Interchange Format files. dif

Symbolic Link Format text files. slk

dBase Data Files. dbf

OpenOffice Files. ods

XML Paper Specification Files. xps

Portable Document Format files. pdf

Note that this isn’t an exhaustive list. Excel can open files with other extensions, including html.

How to Fix the “Excel Cannot Open the File Because the File Format or File Extension Is not Valid” Issue on Windows 10

Sometimes, when opening a file in Excel, the program displays this error message instead:

Microsoft Excel

Excel cannot open the file [File Name] 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.

If you encounter this error in any version of Excel since Excel 2007, three options are open to you:

  1. Check the file extension and change it if needed.
  2. Repair the file with Excel’s inbuilt repair tool.
  3. Change group permissions for the file.

Let’s explain each option in more detail.

Solution 1. Check the File Extension

If you’re unable to open the file, it could be due to an unsupported file extension. To be frank, this is very rare nowadays since most spreadsheets use a format Excel can open. However, if you’re trying to open the document on a pre-2007 Excel program, you can have issues with certain files.

There are two scenarios here:

  1. The Excel file is not opening in a legacy version of the program.
  2. The file is not opening in Excel because of an unsupported format.

In both instances, the solution is the same. Open any Excel file (or just launch the program and open a blank spreadsheet) and click the File tab. Next, click Open > Browse and locate the file you’re trying to open.

Now, look under the file name field and change the file extension. If you’re trying to open an xlsx document in a legacy Excel version, change the extension to xls. If you’re trying to open a document in an unsupported or less common file format, change the extension to xlsx or xls.

Save the change and then try opening the file again. If everything is done right, the file should open now.

Solution 2. Repair the File

When you get the “Excel cannot open the file because the file format or file extension is not valid” error, it’s likely because the spreadsheet is corrupt. If you manage to open the file anyway, there might be multiple errors and we’re sure you don’t want that. It is better to try repairing the file first and that is exactly what we’re going to do.

  1. Open a blank spreadsheet in Excel.
  2. Select the File tab and click Open.
  3. Hit the Browse button and choose the problematic file.
  4. In the file selection window, click the Open drop-down menu and select Open and Repair.

Excel will attempt to repair the file and then open it.

Solution 3. Change Group Permissions

In rare instances, the “Excel cannot open the file because the file format or file extension is not valid” error happened because the file has special permissions. Removing this permission will allow your Excel program to open it without issues.

Here are the steps to try:

  1. Navigate to the location of the problematic file.
  2. Right-click the file and select Properties.
  3. When the Properties dialog box opens, switch to the Security tab.
  4. In the Security tab, click the Edit button to change permissions got for the file.
  5. A new Permissions dialog box will open. Locate and click the Add button.
  6. Another dialog box will open labeled “Select Users or Groups”. In this box, click the Advanced button.
  7. Click the Find Now button.
  8. Select Everyone under the search results and then click OK.
  9. Click the OK button again to return to the Permissions dialog box. You’ll notice that the Everyone group has been added to the list under “Groups or user names”.
  10. Select Everyone in the “Groups or user names” section.
  11. Under Permissions for Everyone, tick Allow for all the options.
  12. Click Apply and then OK to confirm and save your changes.

After this, the file will no longer be restricted and you should be able to open it in Excel.