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Salesforce Report Export to Excel Shows Warning: File Is in a Different Format Than Specified by the File Extension

Fecha de publicación: Jun 22, 2026
Descripción

After a Microsoft Office update, users may receive the following warning when opening a report exported from Salesforce in XLS format:

"The file you are trying to open, '[filename].xls', is in a different format than the specified by the file extension. Verify that the file is not corrupted and is from a trusted source before opening the file. Do you want to open the file now?"

This warning appears in Microsoft Excel 2007 and later versions.

Solución

This warning is a user-notification feature built into Microsoft Excel 2007 and later. It appears when the actual file format does not match the file extension. When Salesforce exports a report in XLS format, the file is internally formatted as HTML, which triggers this Excel notification. The file is safe to open. Clicking Yes on the prompt opens the file normally. This is not a Salesforce error — it is a Microsoft Excel compatibility warning.

Why This Warning Appears

Excel 2007 and later versions include a format validation check. Because Salesforce generates the XLS export as an HTML document with an .xls extension (for compatibility reasons), Excel detects the mismatch and displays the warning. The content of the file is not corrupted.

Additional Microsoft Support

For more information on this Excel behavior, refer to the Microsoft support articles in the Additional Resources section below.

Número del artículo de conocimiento

000386986

 
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