ROT13 Encoder/Decoder — Free Online ROT13 Cipher
Encode and decode text with the ROT13 cipher — rotates each letter by 13 positions. ROT13 is its own inverse: apply it twice to get the original text.
Frequently Asked Questions
ROT13: The Classic Text Rotation Cipher
ROT13 is the simplest cipher in practical use. It was invented for Usenet newsgroups in the 1980s as a way to hide spoilers, offensive jokes, or puzzle answers so they could only be read by someone who actively chose to decode them. It has zero security value — a determined reader needs about 2 seconds to decode ROT13 manually.
The algorithm: replace each letter with the one 13 positions later in the alphabet, wrapping around. A→N, B→O, ..., M→Z, N→A, O→B, ..., Z→M. Lowercase follows the same pattern. Numbers, spaces, and punctuation pass through unchanged. Because the English alphabet has 26 letters and 13+13=26, ROT13 is perfectly self-inverse — applying it to encoded text gives back the original.
ROT13 appears in CTF (Capture The Flag) challenges, obfuscated code, light-hearted text puzzles, and occasionally in real codebases for non-sensitive obfuscation. On this tool, "Encode" and "Decode" do the same thing — the distinction only matters for the direction toggle, which has no effect on the result.