How to password protect a Word document
- Drop a
.docxor.docmfile onto the drop zone above, or click to choose it. - Type the Password that people will need to open the document.
- Click Protect document. Deriving the encryption key takes about a second, and a progress indicator is shown meanwhile.
- Download the encrypted copy. A file called
nda-acme.docxis saved asnda-acme-protected.docx.
Everything happens in your browser. The document and the password are never uploaded, which matters when the file is a contract, a disciplinary letter or an unpublished manuscript.
What kind of protection this is
The tool applies the same protection as Word's File > Info > Protect Document > Encrypt with Password. It uses ECMA-376 Agile Encryption, the format Microsoft Office 2010 and later and LibreOffice use for password-protected files:
- The whole document, including text, images, comments and tracked changes, is encrypted with AES-256 in CBC mode.
- The key is derived from your password with SHA-512, repeated 100,000 times, which makes each password guess slow for an attacker.
- An HMAC integrity check lets Word detect whether the encrypted file has been tampered with.
Word has other features with "protect" in the name that do something quite different. It is worth knowing which is which before you send a sensitive file:
| Feature | Content encrypted? | What it actually does |
|---|---|---|
| Encrypt with Password (this tool) | Yes | Nobody can open or read the file without the password |
| Restrict Editing | No | Limits changes to comments, tracked changes or form fields; anyone can still read the text |
| Mark as Final | No | Shows a banner discouraging edits; any reader can dismiss it |
If the goal is confidentiality, only encryption helps. Restrict Editing and Mark as Final are about controlling changes between colleagues, not about keeping the content private.
Who can open the protected file
Word 2010 and later, Microsoft 365, Word for Mac and LibreOffice Writer all ask for the password when the file is opened. Google Docs and many file previewers, including attachment previews in some email clients, cannot open encrypted Office files, so recipients should download the file and open it in a desktop word processor. Old .doc files are not supported: open them in Word and save as .docx first.
Tips
- Use a long, unique password, for example one made with the password generator. The key derivation slows down guessing but cannot save a password like "contract1".
- If the recipient only needs to read the document, convert it with Word to PDF and then encrypt the PDF with Protect PDF.
- Combine several documents first with Merge Word so you only manage one password.
- To remove the password later, use Unlock Word with the same password.
Frequently asked questions
Can a forgotten Word password be recovered?
Not with this site. Our tools never crack or guess passwords, and AES-256 encryption is designed so that the content cannot be read without the correct password. Treat a lost password as a lost document.
Will macros in a .docm file still work?
The tool accepts .docm files and encrypts the whole document package. After the password is entered, Word opens the file as it was before.
Why can't my colleague open the file in Google Docs?
Google Docs does not open password-encrypted Word files. Your colleague needs Word or LibreOffice, or you can send a version with the password removed through a secure channel.
Can I protect an old .doc file?
No. Binary .doc files use an outdated encryption scheme. Save the file as .docx in Word or LibreOffice and protect that copy instead.