What is ROT13?
ROT13 (Rotate by 13 places) shifts each letter 13 positions forward in the alphabet: A becomes N, B becomes O, and so on. Because the alphabet has exactly 26 letters, applying ROT13 twice returns the original text — encoding and decoding are the identical operation. It was widely used on early internet forums to hide spoilers and jokes without removing them entirely. ROT47 extends the same idea to all 94 printable ASCII characters, shifting each by 47 positions.
How to use this tool
- 1 Choose ROT13 (letters only) or ROT47 (all 94 printable ASCII characters) from the toggle.
- 2 Type or paste text into the Input panel — the output appears instantly.
- 3 Applying the cipher again decodes it — both modes are self-inverse. The Swap button copies the output back to input for a second pass.
- 4 Click the copy icon to grab the result.
Frequently asked questions
Is ROT13 a secure cipher?
No. ROT13 provides zero security — anyone who knows the algorithm can decode it immediately without a key. It was designed for trivial obfuscation, not secrecy. For actual encryption, use AES-256 or another modern algorithm.
Why is applying ROT13 twice the same as doing nothing?
ROT13 shifts by 13. The alphabet has 26 letters. Shifting by 13 twice gives a shift of 26, which wraps back to 0 — the original position. This self-inverse property is why the same function encodes and decodes.
What does ROT47 cover that ROT13 does not?
ROT13 only rotates letters (A-Z and a-z). Digits, punctuation, and symbols are unchanged. ROT47 rotates all 94 printable ASCII characters from ! (33) to ~ (126), so digits and symbols are also shifted. ROT47(ROT47(x)) = x for the same reason as ROT13.
What was ROT13 used for historically?
Usenet newsgroups in the 1980s and 1990s used ROT13 to hide punchlines, offensive content, and movie spoilers. Readers who wanted to see the text would run it through ROT13; those who did not could scroll past. It was a social convention, not a technical security measure.
Is my text sent to a server?
No. ROT13 and ROT47 are pure string transformations that run entirely in your browser. No data is transmitted.