ROT13 Decoder & Encoder
Paste text and convert it with ROT13 instantly. Because ROT13 shifts every letter by exactly half the alphabet, the same operation encodes and decodes — one box does both directions. Everything runs in your browser; nothing is uploaded.
ROT13 is its own inverse — paste either side here.
The converted text appears here.
What Is ROT13?
ROT13 (“rotate by 13 places”) is a Caesar cipher with the shift fixed at 13: A↔N, B↔O, C↔P, and so on. Since 13 is exactly half of the 26-letter alphabet, running the transformation twice moves every letter a full 26 places — right back where it started. That self-inverse property is the whole point: there is no key to remember and no separate decoder, which made ROT13 the standard way to hide spoilers, puzzle answers, and joke punchlines on Usenet in the 1980s, a tradition that continues on forums, newsletters, and geocaching pages today.
How to Use This Converter
- Paste your text — spoiler text you want to read, or plain text you want to hide.
- Read the result — it converts as you type. Letters rotate; numbers, spaces, and punctuation pass through, and capitalization is kept.
- Copy it with the copy button and paste it wherever the spoiler goes.
Worked Example
Gur ohgyre qvq vg converts to The butler did it— and pasting the answer back in returns the original ROT13. Try it with your own text: encode, then encode again, and you’ll get your starting text back. That round trip is a handy sanity check that no characters were lost.
ROT13 Is Not Security
ROT13 has no key and everyone knows the algorithm, so it provides literally zero confidentiality — the phrase “double ROT13” is a running joke among programmers precisely because it does nothing. Use it to be considerate (hiding a spoiler from someone’s glance), never to be secret. If you’re curious about ciphers that at least require some cracking effort, start with the Caesar cipher decoder (25 keys) and the cryptogram solver (a full substitution alphabet).
Frequently Asked Questions
What is ROT13?
A Caesar cipher with a fixed shift of 13. A becomes N, N becomes A. It’s the traditional way to hide spoilers in plain sight online.
Why is ROT13 its own inverse?
Shifting by 13 twice equals shifting by 26 — a complete lap around the alphabet. Encoding and decoding are the same operation.
What is ROT13 used for?
Spoilers, riddle hints, puzzle answer keys, and punchlines — anywhere you want text unreadable at a glance but instantly reversible.
Is ROT13 real encryption?
No. There’s no key and no secrecy. It’s a courtesy curtain, not a lock.
What happens to numbers and punctuation?
They pass through unchanged. Only A-Z and a-z rotate, and case is preserved.
What’s ROT47?
A variant that rotates all 94 printable ASCII characters, so digits and symbols change too. This page implements classic ROT13, the spoiler standard.
Does my text leave my browser?
No. The rotation happens client-side in JavaScript; nothing is sent anywhere.
Make a Puzzle Out of It
Want to hand someone a printable decoding challenge instead of a link? The free cryptogram maker turns any quote into a substitution-cipher worksheet with an answer key.
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