Password Protect a Word Document
Upload a .docx file, set a password, and get back an AES-encrypted Word document — same format, same extension, no ZIP wrapping. It is the same encryption Word applies at File → Info → Protect Document → Encrypt with Password.
Word's two password types — only one is real encryption
Password to Open (real encryption)
This is what our tool applies. The whole document is encrypted with AES. Without the password the file is unreadable — Word will not even show a preview. This is cryptographically meaningful protection.
Password to Modify (soft lock)
This is NOT encryption. The document opens as read-only, but anyone can view all of its content. The password only blocks editing, and it is trivially bypassed: open as Read-Only, then Save As a new file. Or unzip the .docx and delete the writeProtection element in settings.xml.
What about Track Changes, comments, and metadata?
Word encryption protects the document body — text, images, formatting. Some metadata survives outside the encrypted envelope:
- Document properties (title, author, last saved by) are visible in File Explorer → Properties without opening the file. Use File → Info → Inspect Document to remove them before encrypting.
- Track Changes history is encrypted inside the document body, so it is safe. But if you shared the document before encrypting, earlier versions may still be floating around.
- File size reveals document length. A 5 KB .docx is obviously a one-pager; a 500 KB .docx signals substantial content. Anyone can see the file size without opening it.
Encryption strength by Word version
| Format | Cipher | Strength | Recovery risk if password lost |
|---|---|---|---|
| .doc (Word 97-2003) | 40-bit RC4 | Weak | Finite-key candidate; verify the exact variant before recovery |
| .docx (Word 2007) | AES-128, SHA-1, 50K iter | Moderate | Dictionary passwords recoverable; random passwords survive |
| .docx (Word 2010) | AES-128, SHA-512, 100K iter | Moderate | Similar to 2007 but slower to attack per guess |
| .docx (Word 2013+) | AES-256, SHA-512, 100K iter | Strong | Only weak/repeated passwords recoverable |
Our tool applies the strongest encryption compatible with your file — AES-256 for .docx. If you're working with an old .doc file, save as .docx first (File → Save As → Word Document) to get strong AES encryption instead of weak 40-bit RC4.
Frequently asked questions
Does encrypting a .docx change the file format?
Is this the same encryption Word applies itself?
What happens if I forget the password I set?
Encrypt a Word document
Free, no signup. The output stays a real .docx with AES-256 encryption applied.
For authorized owner use only. Recovery depends on the exact file and password; no outcome is guaranteed. FilesUnlock is a separate product from the recovery service that processes submissions.