Renamed Microsoft Excel Spreadsheet
3.3 | 16 Votes
What is a _XLSX file?
An _XLSX file is a Microsoft Excel spreadsheet that has had its extension changed from .XLSX to ._xlsx. A user or program may have changed the file's extension on purpose or by accident. _XLSX files can be opened in Microsoft Excel and other spreadsheet programs after you rename them to use the .xlsx extension.
_XLSX files are almost always renamed XLSX files. Most commonly, email programs such as Windows Live Mail mistakenly produce _XLSX files. This happens when a user attaches a spreadsheet whose filename ends in . to an email.
For example, if you attach a spreadsheet named spreadsheet..xlsx to an email, Windows Live Mail will rename that file to spreadsheet._xlsx. This issue also occurs when users attach .DOC, .DOCX, and .XLS files to emails.
While XLSX, and thus _XLSX, files are typically created by Microsoft Excel, they can also be created using other spreadsheet programs, such as OpenOffice Calc or Apple Numbers. After renaming your _XLSX file to use the .xlsx extension, you should be able to open the file in any of those programs.