How to Fix Excel File Format and Extension Mismatch on SharePoint
Question details
The user needs to resolve the Excel compatibility warning that appears when a SharePoint workbook has a file format and extension mismatch.
- Product
- Microsoft Excel on SharePoint
- Device & OS
- not provided
- Scenario
- A user opens an Excel file from a SharePoint document library and receives a warning that the file format and extension do not match.
- Observed behavior
- Excel displays the format and extension mismatch warning, and the file may be treated as untrusted until the user confirms it is safe.
Before opening the file, verify the SharePoint document source and file extension. If you do not recognize the sender or location, inspect the file in a safe environment instead of enabling editing.
Verify the file source and open it only when trusted
Use this first when Excel displays the format and extension mismatch warning for a SharePoint file.
Open the SharePoint document library and confirm the file name, extension, and the person or team who uploaded it.
Click the file to open it. When Excel shows the format and extension mismatch warning, select Yes only if you trust the source and expected an .xls file.
After the workbook opens, review the visible content and formulas. If everything matches the intended workbook, click Enable Editing in the protected view bar.
Remove the Windows file block from a downloaded copy
Use this when the SharePoint file has been downloaded and Windows is blocking it as an untrusted file.
Update Office and use a trusted location for verified files
Use this if warnings persist for files that you know are legitimate and you want to reduce false prompts.
Open Excel Workbooks in WPS Office Without SharePoint Format Mismatch Warnings
If the warning is tied to Microsoft Excel and SharePoint, WPS Office gives you a free, lightweight alternative. WPS Spreadsheet opens XLS and XLSX files directly with full format compatibility and a familiar interface, so you can review and edit workbooks without SharePoint trust prompts.
- 1. Download WPS Office: Go to the official WPS Office website and download the free installer for your Windows or macOS device.
- 2. Install and open WPS Spreadsheet: Run the installer, launch WPS Office, and click WPS Spreadsheet to create or open a workbook.
- 3. Open the Excel file locally: Click Menu > Open, select the downloaded XLS or XLSX file, and review it without SharePoint extension mismatch warnings.
- 4. Edit and save in Excel format: Make your changes, then click Menu > Save As and choose Excel Workbook (*.xlsx) to keep Microsoft Excel compatibility.
Frequently Asked Questions
Why does Excel show the file format and extension mismatch warning on SharePoint?
The file content may be HTML, XLA, or another format saved with an .xls extension, or Windows/SharePoint may treat the file as untrusted. Excel warns before opening it to protect your computer.
Can I still open an Excel file after this warning?
Yes, but only if you trust the source. Confirm the file uploader and extension first, then click Yes in the warning dialog and enable editing after checking the workbook content.
How do I unblock a downloaded SharePoint Excel file in Windows?
Right-click the file, choose Properties, open the General tab, check Unblock, and click Apply and OK. Then reopen the workbook in Excel.
Will WPS Office open XLS and XLSX files without this SharePoint warning?
WPS Spreadsheet can open XLS and XLSX files directly from local storage, so SharePoint trust warnings do not appear. You should still verify any file source before opening it.
Does WPS Office keep Excel formulas and formatting?
Yes, WPS Spreadsheet supports Excel formulas, charts, pivot tables, and formatting, and can save in .xlsx format for Microsoft Excel compatibility.
