ROT13 Decoder & Encoder
Paste text and it is rotated by 13 letters. Paste the result back and you get the original — ROT13 is its own inverse.
Why doing it twice undoes it
Split the alphabet into two halves of 13. ROT13 simply swaps each letter with the one directly below or above it. Swap twice and every letter is back where it started.
That symmetry only works because 13 + 13 = 26. A Caesar shift of 3 needs a shift of 23 to undo it; ROT13 is the one shift that is its own reverse.
Questions people ask
What is ROT13?
ROT13 (“rotate by 13 places”) replaces each letter with the letter 13 positions after it in the alphabet. Because the alphabet has 26 letters, doing it twice returns the original text, so one button both encodes and decodes.
What is ROT13 used for?
Hiding spoilers, puzzle answers and punchlines so they are not read by accident. It became a convention on Usenet in the early 1980s. It offers no security at all.
What is ROT47?
ROT47 rotates all 94 printable ASCII characters (from ! to ~) by 47 places, so digits and punctuation are scrambled too. Like ROT13, applying it twice restores the text.
Does ROT13 change numbers?
No, only the letters A–Z and a–z. Use ROT47 if you want digits and symbols changed as well.