Encrypt a File
Lock a file with a password using AES-256, entirely in your browser.
About this tool
Choose a file, set a password, and get back an encrypted copy that only that password opens. Decryption is the same tool in reverse. Everything happens in the page using the browser's own cryptography โ the file is never uploaded and the password is never transmitted or stored.
What it actually does
The password is put through PBKDF2 with 250,000 rounds of SHA-256 and a random 16-byte salt to derive a 256-bit key. That key encrypts the file with AES-GCM using a random 96-bit nonce.
Each piece matters. The salt means two people using the same password get different keys, which defeats precomputed tables. The 250,000 rounds make each password guess expensive โ the delay you notice is the point. AES-GCM is authenticated, so a file altered after encryption fails to decrypt rather than quietly producing corrupted output.
The strength ultimately rests on your password. AES-256 is not the weak link; a guessable password is. Use a long passphrase.
The limits, stated plainly
- There is no recovery. Nobody, including this site, can open the file without the password. Forget it and the contents are gone.
- The output only opens here. The file header is specific to this tool. For something a recipient can open with standard software, use 7-Zip, GPG, or your operating system's own encryption.
- The filename is not hidden. Only the contents are encrypted.
- This protects a file at rest, not a compromised device. If something is reading your keystrokes, no amount of encryption helps.
Frequently asked questions
Is it safe to encrypt a file on a website?
It depends entirely on whether the encryption happens locally. This one runs in your browser using Web Crypto โ you can disconnect from the internet after the page loads and it still works, which is a reasonable way to check the claim.
What happens if I forget the password?
The file cannot be opened. There is no reset, no backup key and no recovery โ that is what makes the encryption meaningful. Store the password in a password manager.
What encryption does it use?
AES-256-GCM, with the key derived from your password by PBKDF2 using 250,000 rounds of SHA-256 and a random salt. GCM also detects tampering, so an altered file fails to decrypt rather than producing garbage.
Can the recipient open it without this tool?
No โ the file format is specific to this tool. If they need to open it with standard software, use 7-Zip or GPG instead.
Is the file uploaded to encrypt it?
No. It is read into memory, encrypted locally, and saved straight back to your device.