Free Online ROT13 Cipher – Encrypt & Decrypt Text Instantly
ROT13 is symmetric — encoding and decoding are the same operation. Also supports ROT5, ROT18, and ROT47 variants.
ROT13 is self-inverse: applying it twice returns the original text.
What is the ROT13 Cipher?
ROT13 (Rotate by 13) is a simple letter substitution cipher that replaces each letter with the letter 13 positions after it in the alphabet. Since the alphabet has 26 letters, rotating by 13 is self-inverse — applying ROT13 twice returns the original text. Encoding and decoding are the same operation.
ROT13 is a special case of the Caesar cipher with a fixed shift of 13. It was widely used in Usenet newsgroups in the 1980s–90s to hide spoilers, jokes, and offensive content from casual readers.
ROT13 Variants Explained
Shifts each letter A–Z by 13 positions. Numbers and punctuation unchanged. Most common and widely recognised variant.
Shifts digits 0–9 by 5 positions (0↔5, 1↔6… 4↔9). Letters and punctuation unchanged. Symmetric like ROT13.
Combines ROT13 for letters and ROT5 for digits simultaneously. Both characters and numbers are rotated in one pass.
Shifts all printable ASCII characters (! through ~, codes 33–126) by 47. Letters, numbers, and punctuation are all rotated.
Encoding Examples
How to Use This ROT13 Cipher Tool
Select ROT13 (letters), ROT5 (digits), ROT18 (both), or ROT47 (all printable ASCII).
Type or paste any text. With Live Mode on, it converts as you type automatically.
Click "Apply ROT13" or use Ctrl+Enter. The same button both encrypts and decrypts.
Click Swap to move output back to input, then apply again — you'll get the original text back.
Copy the result or download it as a .txt file containing both original and ciphered text.
Click any "Try This" button in the examples section to instantly load and apply ROT13.
Who Uses ROT13?
Reddit, forums, and online communities use ROT13 to hide plot spoilers so readers can choose whether to decode them.
Learn classical cipher concepts, substitution tables, and the basics of symmetric cryptography.
Test string manipulation, character encoding, and cipher algorithm implementations in code.
Escape rooms, ARGs, and treasure hunts use ROT13 as a recognisable and solvable puzzle layer.
Embed hidden messages in stories, social posts, or ARG narratives with a well-known encoding.
Understand the concept of symmetric ciphers and rotation-based substitutions as a stepping stone to modern cryptography.
Frequently Asked Questions
Is my text sent to any server when using this tool?
Why is there only one button — doesn't ROT13 have separate encrypt and decrypt?
What is the difference between ROT13, ROT5, ROT18, and ROT47?
What happens to numbers, spaces, and punctuation with ROT13?
Is ROT13 secure for protecting sensitive data?
What is the history of ROT13?
What is Preserve Case option?
A→N, a→n. The output maintains the same capitalisation pattern as the input. If disabled, all output is forced to uppercase.