Hiding isn't the same as protecting
Hiding a sheet only removes it from the visible tab list β anyone who opens the file can unhide it in a few clicks, or reference its data indirectly through formulas on other sheets. For genuinely sensitive data, combine hiding with sheet or workbook protection (a password), or remove the data entirely before sharing the file.
"Very Hidden": a stronger option
Excel actually has a deeper hidden state, sometimes called "Very Hidden," that can only be set or cleared through the VBA editor (Alt+F11). A sheet in that state doesn't even appear in the normal right-click Unhide list, which makes it useful for helper sheets you don't want casual users stumbling into.
Frequently Asked Questions
If I hide a sheet, are the formulas in it still active?
Yes β hiding only affects visibility. Any formulas on that sheet, and any formulas elsewhere referencing it, keep working exactly as before.
Can someone still access a hidden sheet's data without unhiding it?
Yes, indirectly β formulas on visible sheets can still reference and display values from a hidden sheet, so hiding alone doesn't fully block access to the data behind those numbers.