Secure File Tool

Encrypt or decrypt files locally with AES-256-GCM.

100% browser-side — totally secure. Your file and secret key never leave your device. Nothing is uploaded to any server. All encryption and decryption runs entirely in your browser using the native Web Crypto API.

Select a file to detect encrypt or decrypt.

How it works

  1. Select a file — the tool reads it in memory. Plain files are marked for encryption; files starting with AES256ENC: are marked for decryption.
  2. Enter your secret key — the browser hashes it with SHA-256 to derive a 32-byte AES key. Your raw password is never stored.
  3. Click Download — the file is encrypted or decrypted with AES-256-GCM, then saved to your device. Encrypted files include a test verification block so the key is checked before decryption.

Open this page over https:// or localhost — Web Crypto requires a secure context. You can disconnect from the internet after loading the page; everything still works offline.