Encrypt a file with a password
Lock any file (a PDF, photo, video or document) with a password before you email it, put it on a USB stick or store it in the cloud. Only someone with the password can open it.
To encrypt a file with a password, type a strong password above, then choose the file. You get a .locked copy encrypted with AES-256-GCM. To open it again, come back to this page, type the same password and choose the .locked file. Nothing is uploaded.
How to encrypt and decrypt a file
- Type a strong password. A random passphrase is ideal.
- Choose the file. You get a copy ending in .locked; the original isn't changed.
- Send or store the .locked file. Share the password a different way, for example by phone call rather than in the same email.
- To open it: on this page, type the same password and choose the .locked file. The original file comes back with its name.
How the encryption works
Your password is stretched into a 256-bit key with PBKDF2-SHA256 over 600,000 rounds and a random salt, which makes guessing passwords slow. The file is then encrypted with AES-256-GCM, which also detects tampering: if a single byte of the .locked file is changed, it refuses to decrypt instead of giving you a corrupted file. Everything runs through your browser's built-in Web Crypto, on your device.
| Part | What it does |
|---|---|
| AES-256-GCM | Encrypts the file and detects any change to it |
| PBKDF2-SHA256, 600,000 rounds | Turns your password into a key and slows down guessing |
| Random salt and IV per file | The same file and password never produce the same output |
Keep them locked, offline
Sealcloak encrypts your photos, videos and files on your phone. No account, no cloud, no internet permission.
Private by design
The file is read, encrypted and saved inside this browser tab. It's never sent to a server, and the password is never stored. That also means nobody can recover a forgotten password, including us, so keep it somewhere safe.
For files on your phone
This tool is for one-off files you send or store elsewhere. For photos, videos and documents you keep on your Android phone, Sealcloak does the same kind of protection automatically: every file is encrypted with AES-256-GCM as you add it, inside vaults that open with your own pattern, and it can make passphrase-locked packages for sharing.
Frequently asked questions
How secure is the encryption?
It uses AES-256-GCM with a key derived from your password by PBKDF2-SHA256 over 600,000 rounds. With a strong password, the file can't realistically be opened without it. A weak password is the main risk.
What happens if I forget the password?
The file can't be opened. The password isn't stored anywhere and there's no reset or backdoor, which is exactly what keeps the file private.
How does the other person open the file?
They open this page, type the password and choose the .locked file. It decrypts in their browser and gives back the original file with its name.
Is my file uploaded?
No. Encryption and decryption happen in your browser on your own device. The file and the password are never sent anywhere.
Is there a file size limit?
The limit is your device's memory. Files of a few hundred megabytes work on most computers; very large videos may be too much for a phone browser.
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