The first question is what you can see. A workbook hidden behind an open password is encrypted for opening; a workbook that opens but blocks editing has a different protection layer.
If Excel asks for a password before any worksheet appears, classify it as an open-password case. If the workbook opens and Review shows Unprotect Sheet or Protect Workbook, the restriction is at sheet or workbook level. A tool for sheet protection cannot reveal an unknown password that prevents the file from opening.
Recovery process
If Excel asks for a password before any worksheet appears, classify it as an open-password case. If the workbook opens and Review shows Unprotect Sheet or Protect Workbook, the restriction is at sheet or workbook level. A tool for sheet protection cannot reveal an unknown password that prevents the file from opening.
Record the extension (.xls, .xlsx, .xlsm, or .xlsb), the Excel version, and the exact dialog. Microsoft documents different protection controls for files and for workbook structure, and Excel for Mac has a 15-character limit in some workbook-protection flows. Do not treat that limit as a diagnosis for every open-password error.
Make a working copy and keep the original unchanged. Do not rename an encrypted file or save an XLSM as XLSX to make a prompt disappear: changing the container can remove macros or other features without decrypting the workbook. Submit only a file you own or are authorized to process.
These details help with the first profile check.
The outlook depends on the actual encryption profile.
Common situations
Make a working copy and keep the original unchanged. Do not rename an encrypted file or save an XLSM as XLSX to make a prompt disappear: changing the container can remove macros or other features without decrypting the workbook. Submit only a file you own or are authorized to process.
Next step
Start with format detection and choose the appropriate path only after the file is identified.
Technical details on this page can be checked against the original format or vendor documentation.
