Encrypt File
AES encryption.
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What file encryption actually does
Encrypting a file transforms its bytes into ciphertext that is meaningless without the correct key. Modern tools use AES-256 in an authenticated mode such as GCM, which does two jobs at once: it hides the content, and it detects tampering, so a modified file fails to decrypt rather than silently returning corrupted data.
The key is not your password. A password is stretched into a key by a deliberately slow function — PBKDF2, scrypt, or Argon2 — combined with a random salt stored alongside the file. The slowness is the point: it makes guessing passwords expensive for an attacker. Which means the strength of the whole scheme rests on your password. AES-256 is unbreakable in practice; a six-character password in front of it is not. Use a long passphrase, and understand that nobody, including us, can recover a file whose password is lost.
Why we built this tool
People encrypt files before emailing them, before putting them in cloud storage, before carrying them on a USB stick, and before archiving anything they would not want read if a device were stolen.
Uploading a plaintext file to a website in order to encrypt it is a contradiction: for the duration of that transfer and processing, the unprotected file and often the password itself are on someone else's machine. Ours uses the Web Crypto API — the browser's own audited cryptographic implementation — to derive the key and encrypt entirely in your tab. The plaintext never leaves your device, the password is never transmitted, and there is no server that could hold either. This is the tool where client-side processing stops being a preference and becomes the only sensible design.
Tips and common mistakes
- A long passphrase of unrelated words beats a short complex string, both for strength and for memory.
- Store the passphrase before you encrypt — nobody, including us, can recover it.
- Send the file and the passphrase through different channels.
- Decrypt once immediately to confirm the file works before deleting the plaintext.
Quick start: using Encrypt File
- Load the file you want to protect.
- Choose a long passphrase — several unrelated words beat a short complex string.
- Store that passphrase somewhere safe before you continue; it cannot be recovered.
- Run the encryption and download the encrypted file.
- Decrypt it once immediately to confirm it works, then delete the plaintext if you no longer need it.
Decrypt with Decrypt File. Send the passphrase through a different channel from the file itself.