ROT13
Apply the classic ROT13 substitution cipher — letters shifted by 13 positions in the alphabet.
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About ROT13
ROT13 is a simple substitution cipher that shifts each letter 13 positions through the alphabet (A→N, B→O, …, M→Z, N→A, …). It's its own inverse — applying it twice returns the original text. ROT13 has no real cryptographic value but is widely used in online discussions to hide spoilers, puzzle solutions, and offensive content without making it inaccessible.
When to use it
- Hiding spoilers in forum posts and code reviews
- Light obfuscation of jokes, puzzle answers, or trivia
- Demonstrating substitution ciphers for teaching
- Quick reversible obscuring of content
How it works
Each ASCII letter is shifted by 13 modulo 26: A→N (65 → 78), Z→M (90 → 77), and likewise for lowercase. Non-letter characters (digits, punctuation, whitespace, non-Latin scripts) are left unchanged.
Examples
Hello, World!
Uryyb, Jbeyq!
Frequently asked questions
- Is ROT13 secure?
- No. It's trivially reversible (literally by anyone, with no tools) — its purpose is light obscuring, not security.
- Why does it equal its own inverse?
- Because the alphabet has 26 letters and 13 + 13 = 26. Applying ROT13 twice is equivalent to a ROT26 shift, which returns each letter to itself.
- What's ROT47?
- ROT47 extends the idea to all printable ASCII (94 characters), so it also shifts punctuation and digits. Use Caesar cipher with shift=47 over a wider alphabet for that, or visit a dedicated ROT47 tool.