Your files never leave your device

Encrypt Files with a Password

Lock any file with AES-256 into a .mtenc file, and unlock it with the password. Everything runs inside your browser.

⚠️ If you forget the password, the file cannot be recovered by any means. Keep it somewhere safe.
⚠️ Some files exceed 500MB. Processing happens in browser memory, so it may be slow or fail depending on your device.
Private by design — encryption and decryption run on your device via the browser's built-in WebCrypto API. Neither your files nor your password are ever uploaded, and since we never see the password, we cannot decrypt your files either.

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File Encryption FAQ

How secure is this?

Files are encrypted with AES-256-GCM, the same standard used by banks and governments. Your password is stretched into a key with PBKDF2 (SHA-256, 310,000 iterations), which makes brute-force attacks dramatically slower, and the GCM authentication tag detects any tampering. The final strength depends on your password though — use a long, unpredictable one.

Is the file format open? Can I decrypt without this site?

Yes — it is fully documented, not proprietary. The layout is MTENC1 magic (6 bytes) + salt (16 bytes) + filename length (2 bytes, big-endian) + original filename (UTF-8) + IV (12 bytes) + AES-256-GCM ciphertext (16-byte auth tag included). The key is PBKDF2-HMAC-SHA256 with 310,000 iterations. The original filename is stored in the header so it can be restored; the contents are fully encrypted. Anyone can implement this with standard WebCrypto or OpenSSL, so your files stay recoverable even if this site disappears — as long as you have the password. Without it, not even we can decrypt them.

What if I forget the password?

There is no way to recover the file. There is no master key, no backdoor, and nothing stored on any server — if the password is lost, the file cannot be recovered by any means. Keep your password somewhere safe.

Are my files uploaded anywhere?

No, nothing is ever sent anywhere. All encryption and decryption runs on your device through the browser's built-in WebCrypto API — once the page is loaded, it even works offline. Neither files nor passwords leave your browser.