How to password protect a ZIP file
- Drop the ZIP onto the drop zone above, or click to choose it.
- Type the new Password. A length of 12 characters or more is much harder to guess.
- Choose the Encryption: AES-256 (the default) or ZipCrypto.
- If the ZIP already has a password, enter it under Current password (only if already encrypted). This is how you change a ZIP's password.
- Click Protect ZIP. The result is saved as the original name plus
-protected.zip.
The archive is unpacked and re-encrypted by zip.js in your browser. Neither the files nor the password are sent anywhere.
AES-256 or ZipCrypto?
The ZIP format has two common encryption methods, and the choice is a trade-off between security and which programs can open the result.
| AES-256 | ZipCrypto | |
|---|---|---|
| Strength | Strong, modern encryption | Weak legacy scheme from the 1990s |
| Windows File Explorer | Cannot open it | Opens it |
| 7-Zip, WinRAR, Keka and The Unarchiver (macOS) | Open it | Open it |
| Use it for | Anything that genuinely needs protecting | Casual privacy when the recipient only has Explorer |
ZipCrypto has well-documented weaknesses. An attacker who knows part of the content of one file in the archive, such as a standard file header, can often recover the keys without knowing the password at all. Treat it as a lock that keeps out casual eyes, not as protection for financial, medical or legal documents. AES-256 has no such shortcut, so its security comes down to the strength of your password.
What ZIP encryption does not hide
ZIP encryption protects the contents of each file, but the archive's directory stays readable. Anyone can see the file names, folder names and sizes without the password. A file called 2026-salary-review.xlsx reveals a lot even if nobody can open it.
If the names themselves are sensitive, use a nested archive: first pack the files into a ZIP with Create ZIP, give it a neutral name, then encrypt that ZIP as a single file with Password Protect Any File. The outer listing then shows only one innocuous file name.
Tips
- Generate a long random password with the password generator and send it through a different channel than the ZIP, for example by text message rather than in the same email.
- To protect loose files or folders rather than an existing ZIP, go straight to Password Protect Any File.
- To take a password off again, use Remove ZIP Password.
- For a single PDF, Protect PDF encrypts the document itself, so it opens with a password in any modern PDF reader.
Frequently asked questions
Why can't Windows open my protected ZIP?
File Explorer does not support AES-256 ZIPs. Ask the recipient to use 7-Zip or WinRAR, or re-protect the original with ZipCrypto if a weaker lock is acceptable.
How do I change the password of a ZIP?
Enter the old password in Current password (only if already encrypted) and the new one in Password, then click Protect ZIP.
Can people see what is in the ZIP without the password?
They can see the file names and sizes, but they cannot read the contents. Use the nested-archive approach above to hide names.
Is the original ZIP changed?
No. A new file ending in -protected.zip is created and your original stays as it was.