How to use ROT13 Encoder & Decoder — Free Caesar Cipher Tool
- 1Choose the scheme you need, then encode or decode.
- 2Paste your text into the left-hand box.
- 3The converted result appears on the right — copy it, or press Swap to send it back through the other way.
About ROT13
ROT13 is the simplest cipher still in everyday use, and its charm is the symmetry: shift each letter 13 places forward, and because that is exactly half the alphabet, doing it again brings you home. One function, no key, no direction to get wrong.
It has never been a security measure. It is a politeness convention — a way to put an answer or a spoiler on screen without it being readable at a glance, while anyone who wants it can decode it in a second.
Numbers, punctuation and spacing pass through untouched, and capital letters stay capital, so the shape of the text survives the rotation.
Frequently asked questions
Why is there no separate decode button?
ROT13 is its own inverse. Thirteen is exactly half of 26, so rotating twice lands you back where you started — encoding and decoding are the same operation.
Is ROT13 secure?
Not remotely, and it was never meant to be. It exists to hide text from casual reading — spoilers, puzzle answers, offensive jokes — not from anyone actually trying to read it.
What happens to numbers and punctuation?
They pass through unchanged. Only the 26 letters are rotated, and case is preserved.
Where is ROT13 still used?
Usenet and forum culture, where it was the convention for hiding spoilers, and in puzzles and CTF challenges as a first thing to try on scrambled-looking text.
Is it free?
Yes — unlimited use, no sign-up, no watermark and no limit on how many times you run it.