How Excel password protection works
Excel has used several encryption schemes over the years, and the version your workbook was saved in is the single biggest factor in how recovery goes:
- Excel 97-2003 (
.xls): older RC4 / 40-bit encryption. Weak by modern standards, so recovery is comparatively fast. - Excel 2007 (
.xlsx): AES-128. Stronger, but still reasonable to search. - Excel 2010: AES-128 with a heavier key-derivation step.
- Excel 2013, 2016, 2019 and Microsoft 365: "agile" encryption with AES-256 and roughly 100,000 hashing iterations per guess. Deliberately slow, so strong passwords take far longer and a GPU makes a real difference.
The app detects which version your file uses and handles them all.
Open password vs sheet protection
Excel has two different passwords, and they are not the same:
- The open password encrypts the entire workbook, so the file will not open at all without it. Recovering it is what this edition does.
- Worksheet or workbook protection only restricts editing an already-open file. That is a separate setting, not file encryption, and is outside this edition's scope.
What to expect
It always tries the most likely candidates first, so short and human-chosen passwords are very recoverable across every version.
- Older
.xlsworkbooks are recovered quickly, often almost instantly. - 2013-and-newer
.xlsxworkbooks use slow agile AES-256, so this is where GPU acceleration and the Smart and dictionary methods pay off, testing far more candidates each second.
A long, truly random password on the modern agile-AES format is the one genuinely hard case that no recovery tool can promise to solve; this edition gives it the best possible chance.
Recovery methods
- Dictionary: real words and known password lists, with optional rules for how people modify passwords.
- Smart: masks and patterns for what you remember, such as length, a prefix, or a trailing year.
- Brute-force: every combination, best suited to short passwords.
Part of the Office range
This edition focuses on Excel. If you also need Word, PowerPoint or Access, Krylack Office Password Recovery covers all four Office apps, and the Suite adds archives and PDF as well.
Frequently asked
How do I open an Excel workbook I'm locked out of?
Open the file in the app, choose a recovery method, and let it search for the workbook's open password. Once found, you use it to open the file in Excel normally.
Is my file the older .xls or the newer .xlsx?
The app detects it for you. As a guide, .xls is the older, faster 97-2003 format, while .xlsx is 2007 and later, with 2013 and newer being the slow, strongest kind.
My workbook opens but a sheet is protected and won't let me edit it.
That is a separate worksheet or workbook protection setting, which is different from the password that encrypts the whole file. This edition focuses on recovering the workbook's open password.