ROT13 / Caesar Cipher
Free ROT13 and Caesar cipher tool. Shift letters by any amount. Letters wrap around the alphabet; non-letters are untouched. For puzzles and obfuscation.
Runs in your browserUpdated Apr 26, 2026
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Frequently asked questions
›What's ROT13?
Caesar cipher with a shift of 13. Because the English alphabet has 26 letters, applying ROT13 twice gives back the original — you don't need separate encode/decode.
›Is ROT13 secure?
Not at all — it's a 2,000-year-old cipher with 25 possible shifts. Use it only for spoiler tags or trivial obfuscation, never for security.
›Can I use a different shift?
Yes — pick any number from 1 to 25. ROT13 is just shift=13.
›Are uppercase and lowercase preserved?
Yes — case is preserved through the shift. Numbers and punctuation pass through unchanged.
›Is the tool free?
Yes — fully free, no signup.