Caesar Cipher / ROT13

How to Use

1. Choose Encrypt or Decrypt.
2. Set the shift amount (1-25). Shift 13 is the well-known ROT13 cipher.
3. Type your text — the result updates automatically.

How the Caesar Cipher Works

The Caesar cipher shifts each letter of the alphabet forward by a fixed number of positions, wrapping around from Z back to A. For example, with a shift of 3, A becomes D, B becomes E, and so on. Decrypting simply shifts in the opposite direction. Non-letter characters (numbers, spaces, punctuation) are left unchanged. ROT13 (shift 13) is a special case that is its own inverse — applying it twice returns the original text.

Common Uses

• Learning the basics of classical cryptography and substitution ciphers.
• Lightly obscuring spoiler text, puzzle answers, or joke punchlines (ROT13 is commonly used for this online).
• Quickly encoding or decoding text for puzzles, escape rooms, or educational exercises.

Note: the Caesar cipher provides no real security — it is easily broken and intended for fun, learning, or light obfuscation only.