ROT13 Encoder
Apply the classic ROT13 letter substitution cipher.
Was this tool helpful?
Thanks for the feedback!
ROT13 replaces every letter of the English alphabet with the letter 13 places after it, wrapping round from Z to A. Paste text into this ROT13 encoder and click Apply ROT13 to scramble it; paste scrambled text and click the same button to read it again, because rotating by 13 twice brings every letter back to where it started.
How the substitution works
The alphabet has 26 letters and 13 is exactly half, so the cipher is its own inverse. The two halves of the alphabet simply swap places:
| Plain | ROT13 |
|---|---|
| A B C D E F G H I J K L M | N O P Q R S T U V W X Y Z |
| N O P Q R S T U V W X Y Z | A B C D E F G H I J K L M |
Capitals stay capitals and small letters stay small. Everything that is not a basic Latin letter passes through untouched: digits, spaces, punctuation, emoji, accented letters such as é, and other scripts such as Devanagari.
Example
Hello, World! 123 café becomes Uryyb, Jbeyq! 123 pnsé. The digits and the é are unchanged while c, a and f rotate to p, n and s. A riddle shows why people use it for punchlines: "Why did the chicken cross the road?" turns into "Jul qvq gur puvpxra pebff gur ebnq?", unreadable at a glance but restored the moment anyone runs it through again.
Where ROT13 is still used
- Spoilers and punchlines. Usenet newsgroups adopted it in the 1980s so readers could choose whether to see a joke's answer or a plot twist.
- Puzzle and quiz answers. Setters print the solution in ROT13 so it cannot be read by accident.
- Geocaching hints. Cache listings on geocaching.com encode their hints this way, and the site's decrypt link simply applies ROT13.
- Programming exercises. It is a common first task when learning string handling, and Python even ships a
rot13text codec.
What ROT13 is not
It is not encryption. There is no key, the method is public, and a person can decode a short message by hand in a minute, so never use it to protect passwords, phone numbers or anything private. It also leaves numbers readable: "Call 98450" becomes "Pnyy 98450". For a shift other than 13, the Caesar Cipher tool lets you choose the amount, though that is equally weak. For genuine secrecy use proper encryption software with a strong key from the Password Generator.
Tips
- There is no separate decode mode because none is needed; the one button always does both jobs.
- If the output looks half-scrambled, the original probably mixed English with non-Latin text, which ROT13 skips.
- ROT13 is sometimes confused with ROT47, which also rotates digits and symbols. This page applies ROT13 only.