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ROT13 ("rotate by 13") is a simple letter-substitution cipher popular in online forums and newsgroups for hiding spoilers, punchlines, and puzzle answers from casual view.
This tool encodes or decodes text using ROT13 — since it shifts every letter exactly half of the 26-letter alphabet, running the same operation a second time returns the original text.
How it works
Enter your text and the tool shifts every letter 13 positions through the alphabet, wrapping around from Z back to A. Because 13 + 13 = 26 (a full trip around the alphabet), applying ROT13 to already-ROT13'd text decodes it — there's no separate "decrypt" mode needed. Non-letter characters like numbers, spaces and punctuation are left unchanged.
- Enter text.
- Click Calculate to see your results.
Examples
Encoding a spoiler
"The butler did it" becomes "Gur ohgyre qvq vg". Running ROT13 on "Gur ohgyre qvq vg" again returns "The butler did it".
Who should use it
- Hiding spoilers, punchlines or puzzle answers in forum posts.
- Simple text obfuscation for programming exercises.
Industry applications
- Online forums and newsgroups
- Programming education and puzzles
Advantages
- Extremely simple and fast — the same operation both encodes and decodes.
- Widely recognized convention for hiding spoilers online.
Limitations
- Provides zero real security — trivial to reverse by inspection or by running it again.
Common mistakes to avoid
- Expecting ROT13 to hide information from anyone determined to read it — it's designed for casual obscuring, not real encryption.
- Assuming numbers or punctuation get shifted too — only the 26 letters are affected.
Best practices
- Use ROT13 for spoiler tags, puzzle answers, or light-hearted obscuring — never for anything that needs real confidentiality.
Tips
- If you're not sure whether text is ROT13-encoded, just run it through the tool — real ROT13 text will turn back into readable words.