ROT13 Encoder/Decoder

What is ROT13 Encoder/Decoder?

ROT13 ("rotate by 13 places") is a simple letter-substitution cipher. It replaces each letter with the letter 13 positions after it in the alphabet, wrapping around from Z back to A. A becomes N, B becomes O, and so on. It is a special case of the Caesar cipher, with the shift fixed at 13. Because the alphabet has 26 letters, 13 is exactly half. Shifting twice moves you 26 places, which lands back on the starting letter. For example, Hello, World! becomes Uryyb, Jbeyq!, and Uryyb, Jbeyq! becomes Hello, World! again.

ROT13 Alphabet Chart

How to Decode ROT13 Online

1. 1

   Paste the ROT13 text into the input field.

2. 2

   Read the result: The decoded text appears instantly as you type.

3. 3

   Copy the result with the Copy button.

4. 4

   To encode instead, type plain text. The output is the ROT13 version. The steps are the same either way.

ROT13 Examples

Notice that the digits in ROT13 do not change, and capital letters stay capital.

• Hello becomes Uryyb

• World becomes Jbeyq

• Spoiler becomes Fcbvyre

• ROT13 becomes EBG13

• The quick brown fox becomes Gur dhvpx oebja sbk

How to Decode ROT13 by Hand

You do not need a tool for short messages. Write the alphabet on two lines: 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 To convert a letter, find it on one line and swap it for the letter above or below it. So G becomes T, and T becomes G. Repeat for each letter and leave everything else alone.

Why ROT13 Is Self-Inverse

The alphabet has 26 letters, and ROT13 shifts each one by 13, which is half of 26. Shifting forward 13 places lands on the same letter as shifting back 13 places. So applying ROT13 a second time undoes the first pass. That is why this tool has one field and no separate encode and decode modes. The same transformation handles both directions. It is also the reason 13 was chosen over other shifts: with any other number, you would need a different command to reverse it.

What ROT13 Is Used For

ROT13 hides text from a casual glance. It does not protect it from anyone who wants to read it. Never use ROT13 where real confidentiality matters.

• Spoilers and punchlines: It began on Usenet in the early 1980s to hide jokes and punchlines until readers chose to reveal them.

• Puzzle answers and hints: Puzzle hunts, forums and geocaching hints often use it so solutions are not read by accident.

• CTF challenges and teaching: It is a common first layer in capture-the-flag challenges and a standard example when teaching substitution ciphers.

• Content warnings: Some communities use it to hide text that readers may not want to see right away.

How to Do ROT13 in Code

JavaScript function rot13(str) { return str.replace(/[a-z]/gi, c => { const base = c <= "Z" ? 65 : 97; return String.fromCharCode((c.charCodeAt(0) - base + 13) % 26 + base); }); } console.log(rot13("Hello, World!")); // Uryyb, Jbeyq! Python import codecs print(codecs.encode("Hello, World!", "rot_13")) # Uryyb, Jbeyq! Linux and macOS terminal echo "Hello, World!" | tr 'A-Za-z' 'N-ZA-Mn-za-m' The tr command maps each letter in the first set to the matching letter in the second. Running the same command on the output returns the original text.

ROT13 vs. ROT5, ROT18 and ROT47

ROT13 only touches letters. Related variants cover other characters. All of them are reversible by applying the same operation again. This tool does ROT13 only, so digits and symbols pass through unchanged.

• ROT13: Letters A-Z and a-z. Shift: 13.

• ROT5: Digits 0-9. Shift: 5.

• ROT18: Letters and digits (ROT13 plus ROT5). Shift: 13 and 5.

• ROT47: 94 printable ASCII characters, including letters, digits and symbols. Shift: 47.

ROT13 vs. the Caesar Cipher

The Caesar cipher shifts each letter by a fixed number of places, and that number can be anything from 1 to 25. Julius Caesar is said to have used a shift of 3. ROT13 is the Caesar cipher with the shift set to 13. The difference that matters: with a Caesar shift of 3 you must shift back by 3 to decode, so encoding and decoding are different operations. With 13 they are the same operation.

ROT13 Is Not Encryption

ROT13 has no key and no secret. Anyone who recognises the pattern can reverse it in seconds, by hand or with this tool. It is obscurity, not security. Do not use it to protect passwords, personal data or anything confidential. Use proper encryption for that.

Decode or Encode ROT13 with Bytelify

Use Bytelify's free ROT13 decoder and encoder to reveal a spoiler, solve a puzzle clue or hide an answer in seconds. Type or paste your text, read the result and copy it. Nothing to install, and nothing leaves your browser. Looking for something else? Try the Base64 Decoder, the Morse Code Translator or the Reverse Text Generator.