Decode or encode ROT13 text in one step, or switch to ROT5 for digits, ROT18 for letters and digits, or ROT47 for all printable ASCII.
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Apply twice to undo.
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ROT13 replaces each Latin letter with the one 13 positions further along the alphabet, wrapping around at the end. Applying it a second time restores the original text, so one operation both encodes and decodes.
The three relatives work the same way on different characters:
Because the Latin alphabet has 26 letters, and 13 is exactly half. Rotating by 13 twice returns you to the start, so encoding and decoding are the same operation and one function does both.
Every variant here shares that property. ROT5 works because there are 10 digits, and ROT47 because its character range has 94 positions. Applying any of them a second time restores the original text, which is why there is no separate decode mode.
If the goal is hiding text from someone who might actually look, use real encryption with a key. ROT13 is not that.
If the goal is making text unreadable at a glance, ROT13 is the traditional choice and the Text Flipper is the more visual one. Base64 is also commonly mistaken for obfuscation and is no better at it.
ROT13 is a Caesar cipher, the technique named for its use in Roman military correspondence, where any shift could be chosen. Fixing the shift at half the alphabet is the one refinement that makes it self-inverse.
It has a genuine niche: hiding spoilers, puzzle answers and punchlines in plain text, where the point is that a reader must choose to decode rather than be unable to. Usenet convention made this standard, and it persists.
Warning
There is no confidentiality here whatsoever. A substitution cipher with a fixed, published shift protects nothing, so never use it for passwords or sensitive data.
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