Office Apps Crashing

Fix Excel 365 Crashing After Update & Corrupt File Errors

Huma Ashraf Ch Sep 25, 2026 869 views

Question details

The user is experiencing application crashes when starting Excel 365 following a recent software update, and previously working files are now displaying corrupt file and extension mismatch errors.

How to Fix Excel 365 Crashing After an Update and File Extension Errors

Product: Excel 365
Device & OS: Windows
Scenario: Launching the Excel 365 application or attempting to open existing Excel workbooks after installing system or Office updates.
Observed behavior: Excel 365 unexpectedly crashes during startup. Additionally, older files trigger error messages stating that the file is corrupt or that the file extension does not match the actual file type.

Before you start

Determine if the crash happens when launching the Excel application independently or only when you double-click a specific workbook, and avoid relying on files with sensitive licensing information until they are verified.

Solution 1Recommended

Run an Office Quick Repair

Use the built-in Windows repair tool to fix underlying Microsoft Office installation issues caused by recent updates.

Microsoft 365 updates independently from Windows updates. Occasionally, an interrupted update or system conflict can corrupt Office application files. A Quick Repair scans and replaces these damaged files without requiring a complete reinstallation.

Close open applications

Ensure that all Microsoft Office applications, including Word and Excel, are completely closed.

Open Apps and Features

Click the Windows Start menu, type 'Apps and Features' into the search bar, and press Enter to open your system settings.

Locate Microsoft Office

Scroll down the list of installed applications until you find your Microsoft 365 or Microsoft Office installation, then click on it.

Execute Quick Repair

Click the 'Modify' button. When the repair dialog appears, select 'Quick Repair' and click 'Repair' to begin the process.

Restart Your Computer: Once the Quick Repair is complete, restart your Windows computer before attempting to launch Excel 365 again to ensure all changes take effect.

Solution 2

Isolate the Issue via the Start Menu

Determine whether the crash is caused by a damaged application framework or a single corrupted workbook.

Free Microsoft Office alternative

Use WPS Office to Open Your Spreadsheets When Excel Crashes

If Excel 365 continues to crash or falsely reports your files as corrupt after an update, WPS Office serves as a highly compatible, free alternative. It allows you to immediately access, view, and edit your workbooks without disruptions.

1. Download the software: Visit the official WPS website to download and install WPS Office Free on your Windows computer.
2. Open WPS Spreadsheets: Launch the WPS Office desktop application and select the 'Spreadsheets' module.
3. Access your files: Drag and drop your older Excel files directly into the workspace to bypass Excel 365 errors and continue your work.

Seamlessly open and edit Microsoft Excel file formats, including .xlsx, .xls, and .csv.Lightweight installation that avoids heavy system resource usage and frequent update crashes.Familiar user interface requiring zero learning curve for existing Microsoft Excel users.Completely free to use for essential spreadsheet viewing, data entry, and formatting tasks.

microsoft office alternative - wps office

Frequently Asked Questions

Why does Excel report that my file extension does not match the file type?

This error occurs when the internal structure of a file differs from its extension (for example, an HTML or CSV file improperly saved with an .xls extension), or if a recent Office update introduced a compatibility glitch. Opening the file in a stable environment or repairing your Office installation often resolves it.

Can a recent Windows security update cause my Excel to crash?

Normally, Windows security updates do not affect Microsoft 365, as Office updates independently from Windows Update. However, unexpected system-level conflicts can occasionally arise. Restarting your computer and running an Office Quick Repair usually clears these conflicts.

How do I check which version of Excel 365 I am using?

Open Excel directly from the Start menu, click on 'File', and select 'Account' at the bottom left. Under the 'Product Information' section on the right side of the screen, you will see your Office product name, version, and build number.

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