7z AES-256 Encryption: Protecting Your Archive With a Password

If your archive holds anything sensitive, compression alone isn’t enough — anyone who gets the file can read it. Password protection with AES-256 closes that gap.

What AES-256 encryption does

7-Zip encrypts archive contents with the AES-256 cipher. A password you choose is stretched into an encryption key, and each file’s data is scrambled so that without the password the bytes are unreadable. “256” refers to the key size — strong enough that brute-forcing it with today’s hardware is impractical.

Two levels of protection

An encrypted 7z can protect two different things:

• Contents only. File data is encrypted, but the list of file names stays visible.
• Header encryption. With this enabled, the file names, sizes and structure are hidden too. An outsider sees only an opaque blob until they enter the right password.

For maximum privacy, enable header encryption — otherwise someone can learn a lot from the file list alone, even if they can’t read the contents.

Create an encrypted 7z online

You can do all of this right in your browser:

1. Open the compressor.
2. Add the files you want to protect.
3. Choose the 7Z format.
4. Turn on Password protect and enter a strong password.
5. Optionally check Encrypt file names too to hide the structure.
6. Create and download the archive.

Because the encryption happens locally with WebAssembly, your password and files never touch a server — which is exactly what you want when the point is secrecy.

Choosing a strong password

AES-256 is only as strong as the password you give it. Prefer:

• A long passphrase (four or more unrelated words) rather than a short symbol soup.
• Never reuse a password you use elsewhere.
• Store the password in a password manager — an encrypted archive you can’t open is worse than none.

Read the format comparison to see when 7z beats ZIP and RAR for secure archives.