QuickMergePassword Protect an Excel File
Encrypt an .xlsx workbook so the password is required before any cells can be read. Agile AES-256 encryption runs in this browser tab and the file is never uploaded.
How do I password protect an Excel file?
Drag an .xlsx workbook here
or click to browse — the file is read in this tab and never uploaded
This is password-to-open encryption. The download is an Agile AES-256 encrypted workbook, not a worksheet editing lock. Excel or another compatible spreadsheet app must verify the password before it can read the workbook contents.
Real password-to-open encryption
Excel uses the word protection for two very different features. Worksheet protection only discourages editing and leaves every cell readable. Password-to-open encryption wraps the complete workbook in an encrypted container and withholds its contents until the password is verified.
This tool applies the second kind. The exported workbook uses ECMA-376 Agile encryption with AES-256, SHA-512 password derivation and a random package key. Without the correct password, spreadsheet software cannot read the workbook XML, values, formulas, styles or embedded content.
How to encrypt the workbook
- Drop in an unencrypted .xlsx file. It is parsed in this tab so the tool can confirm it is a workbook and report the worksheet count.
- Enter the password twice. The confirmation prevents a typing mistake from producing a file nobody can open.
- Encrypt and download. The new copy gets
-encryptedin its name. The original file is not changed. - Test the download. Open it in Excel or another compatible app and confirm it asks for the password before showing any cells.
Compatibility and performance
Agile encryption is the modern Office password format and is supported by current desktop Excel and LibreOffice. Some browser-based spreadsheet editors do not accept encrypted Office files, so decrypt the workbook in desktop software before importing it there.
Encryption is deliberately expensive: the password derivation runs 100,000 SHA-512 iterations before AES-256 encrypts the package. Large workbooks therefore take longer on older phones and laptops. Keep this tab open until the download begins.
What this does not do
Encryption controls who can open the workbook. Once someone has the password and opens it, they can normally edit, copy or redistribute the contents. If the separate goal is to stop accidental formula edits in a shared template, use Excel’s Review → Protect Sheet feature as well.
There is no recovery path. The password and file stay on this device, so QuickMerge has no stored copy, reset link or back door. Record the password in a password manager before sharing the workbook.
Nothing is uploaded
The workbook is read, encrypted and downloaded in this browser tab. Neither the file nor password is sent to QuickMerge or the encryption library’s CDN. Verify it from the browser network panel if you would rather not take our word for it.
Next steps
Before this step
- create a strong workbook password — and save it in a password manager before encrypting the only copy.
Related tools
- remove worksheet editing protection — when the workbook opens normally and only cell editing is locked.
- password-protect a PDF instead — when the file you need to secure is a document rather than a workbook.
What to do with the result
- check which kind of protection you need to remove later — password-to-open encryption and worksheet editing flags are different controls.
Browse all text and data tools, or see every QuickMerge tool.