ROT13 / ROT47 Cipher

Encode or decode text using ROT13, ROT5, ROT47, or any custom rotation value. Self-inverse and live.

Last reviewed: April 2026
Reviewed by , software engineer · last updated April 2026

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Input
Output (apply again to decode)

Alphabet mapping (original → rotated):

Type text above to apply ROT13.

How to Use the ROT13 Cipher Tool

The ROT13 Cipher Tool is a free online encoder that allows you to encode or decode text using the ROT13, ROT5, ROT47, or any custom rotation value. To use the tool, simply choose a cipher mode from the options provided, type or paste your text into the input field, and the encoded output will appear in real time on the right. To decode the text, simply apply the same cipher mode again. The tool is self-inverse, meaning that applying the same rotation twice will return the original text.

For example, if you choose the ROT13 mode and type 'Hello, World!', the output will be 'Uryyb, Jbeyq!'. Non-letter characters, such as spaces, digits, punctuation, and symbols, are passed through unchanged. The tool is easy to use and can be accessed from any web browser.

When to Use the ROT13 Cipher Tool

The ROT13 Cipher Tool is still actively used in specific contexts. It is commonly used to hide movie or book spoilers in online reviews and forums, obfuscate email addresses to reduce scraper visibility in source code, mask quiz answers on educational websites, encode clues in puzzle hunts and Alternate Reality Games (ARGs), and as a first example in cryptography courses.

Some Unix and Linux systems include a rot13 command-line utility, and the Python string library even has a built-in ROT13 codec. The tool is a simple and effective way to encode and decode text without the need for any software installation.

Frequently Asked Questions

What is ROT13? ROT13 is a simple letter substitution cipher that rotates each letter of the alphabet by 13 positions. Because the English alphabet has 26 letters, applying ROT13 twice always returns the original text - it is its own inverse.

What is the difference between ROT13, ROT5, and ROT47? ROT5 applies the same rotation concept to digits (0-9), while ROT47 rotates all printable ASCII characters from code 33 (exclamation mark) to code 126 (tilde) by 47 positions. Custom Rotation: The Caesar Cipher Connection The Custom ROTn mode lets you choose any rotation from 1 to 25. This is exactly the Caesar cipher - one of the oldest known encryption techniques, used by Julius Caesar to protect his military communications.

Related Tools

Explore more encoding tools: Caesar Cipher with Brute Force - try all 25 rotations at once with frequency analysis, Base64 Encoder/Decoder - binary-to-text encoding used in email and web, Hash Generator - one-way cryptographic hashing with SHA-256, and Morse Code Translator for a completely different encoding system.

Frequently Asked Questions

ROT13 is a simple letter substitution cipher that replaces each letter with the letter 13 positions after it in the alphabet. Because the alphabet has 26 letters, applying ROT13 twice returns the original text - making it its own inverse. ROT13 is used to hide spoilers and puzzle solutions in online forums. It provides no real security.
ROT13 rotates only letters (A-Z) by 13 positions. ROT5 rotates only digits (0-9) by 5 positions. ROT47 rotates all printable ASCII characters (codes 33 to 126) by 47 positions, including symbols. A combined ROT13+ROT5 is sometimes called ROT18.
No. ROT13 provides no cryptographic security. Any attacker can decode it in seconds. ROT13 is designed for light obfuscation - hiding spoilers or preventing casual readers from seeing answers. For actual security, use AES encryption, bcrypt for passwords, or TLS for network communication.
No. This ROT13 cipher tool runs entirely in your browser using JavaScript. Your text is never sent to any server, there is no logging, and no data collection of any kind.
A custom ROTn cipher lets you choose any rotation value from 1 to 25. For example, ROT3 is the classical Caesar cipher. Only ROT13 is self-inverse; for other values you need to apply the inverse rotation (26 minus the rotation amount) to decode.

Quick reference

ROT13 / ROT47 Cipher Quick Reference
Cipher Shift Value Alphabet Range Common Use
ROT13 13 A-Z (26 letters) Obfuscation in text
ROT47 47 ASCII 33-126 (94 characters) Encoding in online forums
ROT13 13 Case-insensitive Simple data masking
ROT47 47 Includes symbols and numbers Complex text scrambling
ROT13 13 Self-inverse cipher Quick reversibility
ROT47 47 Non-printable ASCII excluded Secure communication