SubstitutionDifficulty: Easy
ROT13
A Caesar cipher with a shift of 13: the same steps encode and decode. No settings, just one click.
Try it
27 characters
Result · ROT13
Frperg zrffntr sbe gur pyho
How it works
- 1The alphabet has 26 letters, so 13 is exactly half. ROT13 moves every letter 13 places along.
- 2The first half of the alphabet swaps with the second: A becomes N, B becomes O, C becomes P, all the way to M becoming Z.
- 3The second half goes back: N becomes A, O becomes B, Z becomes M.
- 4Since 13 + 13 = 26, encoding a message a second time makes it readable again. Numbers and punctuation stay the same.
Example
Hello world
Uryyb jbeyq
Did you know
ROT13 became popular on Usenet discussion groups in the 1980s. People used it to hide punchlines, plot spoilers and puzzle answers so nobody read them by accident. It is no good for real secrets - it is just a Caesar cipher with a fixed shift.
Try to decode
This message is encrypted with ROT13 using the default settings:
ZRRG NG GUR FCEVAT
Hint
The shift is always 13. Try it: N is really A, O is really B.
Show solution
MEET AT THE SPRING
More ciphers in this category
- Caesar cipherEvery letter moves a fixed number of places along the alphabet. The most famous cipher in the world and a perfect first step.
- Vigenère cipherA Caesar cipher with a password: each letter shifts by a different amount set by the keyword. Much tougher than plain shifting.
- Polybius squareLetters in a 5x5 grid, each written as a pair of numbers: row and column. You can tap it, flash it or clap it.
- AtbashThe alphabet flipped like a mirror: A becomes Z, B becomes Y. No key, no settings, and decoding is the same as encoding.