ROT13 Encoder

Apply ROT13 substitution cipher to text — rotate letters by 13 positions. Used for spoilers, puzzles, and obfuscation.

What is ROT13?

ROT13 (Rotate by 13) is a simple letter substitution cipher that replaces each letter with the letter 13 positions after it in the alphabet. It is derived from the Caesar cipher. Because the English alphabet has 26 letters, applying ROT13 twice returns to the original text — encoding and decoding use the exact same operation, making ROT13 its own inverse.

ROT13 is not used for security — it provides no real encryption and is easily reversed by anyone. Instead, it is conventionally used on internet forums and newsgroups to hide spoilers, puzzle answers, and potentially offensive content behind a simple veil that requires a small deliberate action to reveal, preventing accidental exposure.

The transformation only affects letters A–Z and a–z. Numbers, spaces, punctuation, and all other characters are left unchanged. For example: "Hello, World!" becomes "Uryyb, Jbeyq!". The 'H' shifts 13 positions to 'U', 'e' becomes 'r', and so on.

This tool also supports ROT5 (rotates digits 0–9), ROT18 (ROT13 for letters + ROT5 for digits simultaneously), ROT47 (rotates all printable ASCII characters 33–126), and custom rotation amounts for classic Caesar cipher use.

Frequently Asked Questions

Is ROT13 the same as decoding? Do I need a separate decoder?
ROT13 is self-inverse — applying it twice gives back the original text. So encoding and decoding are the same operation. You can use this encoder to decode ROT13 text as well, or use our dedicated ROT13 Decoder page.
What is the difference between ROT13 and Caesar cipher?
Caesar cipher is a generalization of ROT13 where you can choose any rotation amount (1–25). ROT13 is simply the specific Caesar cipher with a rotation of 13. The Caesar cipher was used by Julius Caesar for military communications — he typically used a shift of 3.
What does ROT47 do?
ROT47 rotates all printable ASCII characters in the range 33 (!) to 126 (~) by 47 positions. It covers a wider range than ROT13 — including digits, punctuation, and symbols. It is used in some online communities as a slightly stronger spoiler-hiding method.

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