ROT13 Encoder/Decoder
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ROT13 Encoder/Decoder
The ROT13 Encoder/Decoder applies the ROT13 substitution cipher to your text, shifting every letter 13 positions through the alphabet. Because the Latin alphabet has 26 letters, applying ROT13 twice returns the original text, making the same tool work for both encoding and decoding. It is commonly used to obscure spoilers, puzzle answers, and light-hearted secrets in online forums and messages.
How do I decode ROT13?
Paste the encoded text into the left panel and the decoded text appears on the right. There is no separate decode mode: ROT13 shifts each letter 13 places through a 26 letter alphabet, so shifting encoded text by another 13 lands every letter back where it started. Uppercase and lowercase letters keep their case, and spacing and punctuation are left as they are.
How do I encode text to ROT13?
Type or paste your normal text into the left panel and the ROT13 version appears on the right, ready to copy. To check the result, paste it back into the left panel and you will get your original text.
What are ROT5, ROT18 and ROT47?
They are variants of ROT13 for text that contains more than letters, and you can choose them from the Cipher setting. ROT5 rotates only the digits 0 to 9 by five places. ROT18 combines the two, applying ROT13 to letters and ROT5 to digits. ROT47 rotates all 94 visible ASCII characters, from ! to ~, by 47 places, so letters, digits and punctuation are all scrambled. Like ROT13, each of them undoes itself when applied a second time.
What is ROT13?
ROT13 (rotate by 13 places) is a simple letter substitution cipher that replaces a letter with the 13th letter after it in the alphabet. For example, the letter A would be replaced by the letter N, the letter B would be replaced by the letter O, and so on. ROT13 is a special case of the Caesar cipher, which was used by Julius Caesar to encrypt military messages. The Caesar cipher tool lets you choose any shift value between 1 and 25.
What are the rules of ROT13?
The rules of ROT13 are simple:
- Each letter in the alphabet is shifted 13 places. For example, the letter A becomes the letter N, the letter B becomes the letter O, and so on.
- Uppercase letters are shifted separately from lowercase letters. For example, the letter a becomes the letter n, the letter b becomes the letter o, and so on.
- Non-alphabetic characters, such as numbers and punctuation, are left unchanged.
What is the history of ROT13?
ROT13 is a simple letter substitution cipher that has been used for centuries to encode and decode messages. The cipher is a special case of the Caesar cipher, which was used by Julius Caesar to encrypt military messages. ROT13 is a popular tool for online communication, as it provides a simple and effective way to hide text from prying eyes.
How can I shift letters a value other than 13?
Our Caesar Cipher tool allows you to select a shift value of between 1 and 25. If you would like to shift the letters by a value other than 13, you can use our Caesar Cipher tool and select the desired shift value.
What is ROT13 commonly used for?
ROT13 has several well-known uses across the internet and beyond:
- Hiding spoilers: Online forums and communities commonly use ROT13 to conceal spoilers for films, books, and TV shows so readers can choose whether to decode them.
- Simple text obfuscation: ROT13 provides a lightweight way to obscure text that is not meant to be read at a glance, such as puzzle answers or punchlines. For a different encoding approach, try the Base64 encoder/decoder.
- Puzzle and trivia communities: Geocaching clues, quiz answers, and riddle solutions are often shared in ROT13 to prevent accidental reading.
- Programming exercises: ROT13 is a classic beginner coding challenge for learning string manipulation and character shifting.
Last reviewed: September 2026