If you have sensitive data you'd like to keep from prying eyes in a Microsoft Excel file, the easiest way to protect it is with Excel's built-in password tools.

There are several options available to you to protect your Excel file with a password. Remember that once you protect the Excel file, you cannot open it without entering the password.

A recommended approach to secure your most private documents — whether it’s a PDF, Word file, or Excel spreadsheet — is to lock them with a passcode. While this does help keep sensitive ...

At the file level, you can password protect an Excel workbook in two ways: You can determine who can get in and who can save changes.

Open the spreadsheet you want to protect in Excel, click the "Review" tab and then click "Protect Sheet" in the Changes group to display the Protect Sheet dialog.

Password-Protected Macros Open the Excel worksheet where you wish to place the macro and then activate the Visual Basic for Applications options by turning on the Developer tab.

Anyone can open and view the data, but only those who know the password can modify the contents–you protect the formulas and everything else. But remember, viewers can see the formulas.