ROT13 encoder and decoder
ROT13 replaces every letter with the one 13 places further in the alphabet: A becomes N, B becomes O and so on. Apply it again and you are back at the original, so one tool both encodes and decodes. The conversion runs in your browser and nothing is uploaded.
How it works
-
Paste your text
Type or paste the text in the left box, or open a .txt file. No text to hand? Click Example.
-
Instant result
The result appears as you type. Change the options and see straight away what changes.
-
Copy or download
Copy the result with one click, save it as a file or use it as input for a next step.
Example
Hello world! This is a secret message. becomes Uryyb jbeyq! Guvf vf n frperg zrffntr. Paste that result back in and you get the original sentence.
What changes
Only the letters A to Z and a to z, keeping their case. Digits, spaces, punctuation and letters with accents are left alone.
Where ROT13 is used
- Spoilers and puzzle answers in forums, which readers can decode on purpose.
- Light obfuscation of an e-mail address in a web page, against simple scrapers.
- Programming exercises, since it is the classic first cipher to implement.
Not a secret code
ROT13 offers no protection: the code has no key, and every letter maps to the same letter every time. For anything private, use encrypt text, which uses a password. A shift other than 13, or a keyword, is available in the Caesar cipher.
Frequently asked questions
Why does the same tool encode and decode?
ROT13 shifts every letter 13 places, and the alphabet has 26 letters, so doing it twice brings you back to the start. `Hello` becomes `Uryyb`, and `Uryyb` becomes `Hello`.
Is ROT13 secure?
No. It hides text from a casual glance but anyone can reverse it in seconds, so it is for spoilers, puzzles and jokes. For real secrets use [encrypt text](/en/text/encrypt-text).
What happens to digits, punctuation and accents?
They stay as they are. `Hello, World! 123 é` becomes `Uryyb, Jbeyq! 123 é`; only the letters A to Z are shifted, in both cases.
Is ROT13 a Caesar cipher?
It is a Caesar cipher with a shift of 13. The [Caesar cipher](/en/text/caesar-cipher) tool lets you pick any shift from 1 to 25, and Vigenère and Atbash as well.