1. 01Choose AES, Caesar, ROT13 or rail fence, then pick the encrypt or decrypt direction (ROT13 reverses itself in the same operation).
2. 02For AES enter the passphrase; for Caesar pick a shift of 1–25; for rail fence pick 2–10 rails and the W or group variant.
3. 03Type the text — the result is produced locally in about 200 ms.
4. 04Copy or download the result; decrypting AES needs a compatible format and the correct passphrase.

• AES here is the CryptoJS/OpenSSL-compatible “passphrase string” mode; it does not expose an independent IV, AAD or authentication tag, so it must not be described as AES-GCM.
• AES ciphertext depends on a random salt: the same plaintext and passphrase produce different output every time. A wrong passphrase or an incompatible ciphertext reports a failure.
• Caesar only matches [a-zA-Z]; digits, Chinese text, emoji and punctuation are left untouched.
• Rail fence rearranges by JavaScript Unicode code points, so spaces and punctuation take part as well; decryption needs the same rail count and variant.
• Caesar, ROT13 and rail fence are classical ciphers and encoding puzzles that provide no modern confidentiality; the strength of AES still depends on the passphrase you choose and on CryptoJS-compatible schemes.

Plaintext, ciphertext and passphrases are handled only in browser memory and are never uploaded; sensitive keys still should not be typed on an untrusted device.