🔄 ROT13 Cipher Free & Instant
Encode or decode text – ROT13 is its own inverse, so the same button works both ways.
🔁 ROT13 shifts letters by 13 places. Applying it twice returns the original text.
What is ROT13?
ROT13 (“rotate by 13 places”) is a simple letter substitution cipher that replaces a letter with the 13th letter after it in the alphabet. Because the English alphabet has 26 letters, applying ROT13 twice returns the original text – the same algorithm is used for both encoding and decoding.
It is a special case of the Caesar cipher and was widely used in early online forums to hide spoilers, punchlines, or offensive content behind a trivial obfuscation. Today it remains popular in puzzles and as a gentle introduction to encryption concepts.
How Does It Work?
Only letters A–Z and a–z are changed; numbers, spaces, and punctuation remain untouched. The mapping is:
A ↔ N, B ↔ O, C ↔ P, D ↔ Q, E ↔ R, F ↔ S, G ↔ T, H ↔ U, I ↔ V, J ↔ W, K ↔ X, L ↔ Y, M ↔ Z
Uppercase and lowercase are preserved. For example: Hello → Uryyb, World! → Jbeyq!.
Why Use This Tool?
- Instant conversion – type and see the result live.
- Clean, ad‑free interface – no distractions.
- Works on all devices – mobile, tablet, desktop.
- One‑click copy – easily share the obfuscated text.
ROT13 vs ROT5, ROT18, ROT47
ROT13 only affects letters. To also obfuscate digits, you can combine ROT5 (digits only) to get ROT18. ROT47 covers a larger set of printable ASCII characters. Our tool focuses on pure ROT13 for simplicity and backwards compatibility with traditional forums.
Fun Fact
Because ROT13 is symmetric, many newsgroup readers and IRC clients once included a built‑in “rot13” command. You can still see it in action on some UNIX systems with tr 'A-Za-z' 'N-ZA-Mn-za-m'.
