Codec lesson · ROT13
ROT13: one alphabet, shifted halfway around
ROT13 rotates each Latin letter by 13 places. Because the English alphabet has 26 letters, the same operation both encodes and decodes.
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ROT13 rotates each Latin letter by 13 places. Because the English alphabet has 26 letters, the same operation both encodes and decodes.
A becomes N, B becomes O, and N wraps back to A. Uppercase and lowercase stay in their own ranges. Digits, punctuation, emoji, and non-ASCII letters stay unchanged; ASCII letters inside Vietnamese text still rotate.
How Encode Keyboard handles it
Find a Latin letter
Only A–Z and a–z enter the rotation.
Move 13 positions
The shift wraps around at the end of the alphabet.
Apply again to restore
Two half-alphabet rotations equal one full 26-letter cycle.
Worked example
Hello, world!Uryyb, jbeyq!Punctuation stays put. Running ROT13 again restores the original exactly.
Good uses
- Lightweight word puzzles
- Hiding spoilers at a glance
- Learning substitution ciphers
Validation and common errors
- Only basic Latin letters change
- Letter frequency and structure remain obvious
- Every ROT13 reader can reverse it instantly
Practice in your browser
This uses the same documented rules as the app and runs only in this tab.