ROT13 Encoder & Decoder
Apply ROT13 cipher to encode or decode text. Same function works both ways. Free and instant.
Input Text
Characters
0
Words
0
Output
ROT13 transformed text will appear here
Characters
0
Words
0
Why Use ROT13 Encoder?
Self-Inverse Cipher
Apply ROT13 twice to get the original text back. One function encodes and decodes.
Instant & Free
Transform unlimited text instantly. No sign-up, no waiting, completely free forever.
Preserves Formatting
Only letters are transformed. Numbers, spaces, and punctuation stay unchanged.
What is ROT13?
ROT13 ("rotate by 13 places") is a simple letter substitution cipher that replaces each letter with the letter 13 positions after it in the alphabet. Because there are 26 letters in the English alphabet, ROT13 is its own inverse—applying it twice returns the original text.
ROT13 provides no real cryptographic security; it's trivially easy to decode. Its main use is to hide text from casual viewing—like spoilers in forums or puzzle answers—without preventing determined readers from seeing the content.
ROT13 Alphabet Mapping
Original:
ABCDEFGHIJKLMNOPQRSTUVWXYZ
ROT13:
NOPQRSTUVWXYZABCDEFGHIJKLM
Example:
Hello World → Uryyb Jbeyq
Uryyb Jbeyq → Hello World
Common Use Cases for ROT13
Hiding Spoilers
Forums and discussion boards use ROT13 to hide movie/book spoilers from casual readers.
Puzzle Answers
Hide puzzle solutions or hints so readers can choose when to reveal them.
Email Obfuscation
Obscure email addresses or other text from simple automated scanners.
Usenet Tradition
ROT13 became popular on Usenet newsgroups for hiding jokes and offensive content.
Learning Cryptography
A simple introduction to substitution ciphers and cryptographic concepts.
Fun & Games
Create simple coded messages for games, scavenger hunts, or just for fun.
How to Use the ROT13 Encoder
Enter Your Text
Type or paste the text you want to encode or decode into the input area.
Click Apply ROT13
The same button encodes and decodes—ROT13 is its own inverse.
View Result
See your transformed text instantly with character and word counts.
Copy or Download
Copy the result to your clipboard or download it as a text file.
Frequently Asked Questions
What is ROT13?
ROT13 is a letter substitution cipher that shifts each letter 13 positions in the alphabet.
Is ROT13 secure?
No, ROT13 provides no security. It only obscures text from casual reading, not from anyone trying to decode it.
Why apply ROT13 twice to decode?
Since 13 + 13 = 26 (the alphabet length), applying ROT13 twice returns to the original letter.
What about numbers?
ROT13 only affects letters. Numbers, punctuation, and special characters remain unchanged.
Does case matter?
ROT13 preserves case. Uppercase letters become uppercase, lowercase stay lowercase.
Is my data secure?
Yes, all transformation happens in your browser. No data is sent to any server or stored anywhere.