ROT13 and Caesar Cipher
Encode or decode ROT13 and any Caesar shift from 1 to 25, optionally rotating digits too, with the three most likely decodings of an unknown shift.
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Input
ROT13 and Caesar cipher
Output
Shifted by 13
61 characters
| Shift back | Looks like |
|---|---|
| 13 | Jul qvq gur puvpxra pebff gur ebnq? To get to the other side. |
| 14 | Itk pup ftq otuowqz odaee ftq damp? Sn fds sn sgd nsgdq rhcd. |
| 3 | Tev afa qeb zefzhbk zolpp qeb olxa? Dy qod dy dro ydrob csno. |
ROT13 is its own inverse: applying it twice gives the original, which is why it was used to hide spoilers and punchlines on Usenet. None of this is encryption; 25 possible keys is a guess away, and the likeliest decodings by English letter frequency are listed below. In a shell: tr 'A-Za-z' 'N-ZA-Mn-za-m'.
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About this tool
Method, assumptions, practical next steps, and limits.
ROT13 undoes itself
With 26 letters, shifting by 13 twice returns the original, so the same operation encodes and decodes. That is why Usenet and forums used it to hide spoilers and punchlines: a click reveals them, but the eye does not catch them by accident. In a terminal, tr 'A-Za-z' 'N-ZA-Mn-za-m' does it.
Not encryption
There are only 25 possible keys, so any Caesar cipher is broken by trying them all, which the guesses list does instantly. Use it for obscuring, puzzles and teaching, never for anything that matters.