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ROT13 encoder and decoder

Shift every letter thirteen places. Do it twice and you are back where you started, so one button does both.

Result

The link opens a page that reads it. Without the key, your friend has to crack it. The message travels after the # in the link, which a browser never sends to our server.

ROT13 chart

Every letter, A to Z.

Where it comes from

A shift of thirteen. Because the alphabet has twenty-six letters, doing it twice gives you back the original, so the same step hides and reveals. Early internet forums used it to hide spoilers and punchlines.

A message worth knowing: To get to the other side. Why did the chicken cross the road? By the early 1980s the net.jokes newsgroup hid punchlines in ROT13, so nobody read one by accident.

Learn it by heart

This is the cipher desk from Covert Mail, our free app for learning codes. The app teaches ROT13 a few characters at a time, plans practice around the ones you miss, and keeps an archive of famous real messages to unlock. It is coming soon to the App Store and Google Play.

Coming soon to the App Store and Google Play

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