About ROT13
ROT13 (Rotate by 13) is one of the simplest and oldest text transformations. It replaces each letter with the letter 13 positions ahead in the alphabet: A becomes N, B becomes O, and so on. Because 13 is exactly half of 26 (the number of letters in the English alphabet), the same operation both encodes and decodes — there is no separate "decrypt" step. ROT13 is not encryption and provides no security; it is a convention for obscuring text so it cannot be read accidentally, widely used in Usenet, forums, geocaching, and puzzle communities.
How to Use ROT13 Encoder/Decoder
- Type or paste your text in the Text area — either plain text to encode or ROT13-encoded text to decode.
- Click Encode / Decode. The same button handles both directions.
- The result appears below. Copy it for use in a forum post, message, or puzzle.
Key Features
- Single-button encode and decode — ROT13 is its own inverse
- Processes only A–Z and a–z; numbers, spaces, and punctuation pass through unchanged
- Instant transformation for text of any length
- Perfect for hiding spoilers, puzzle answers, and easter eggs
- 100% browser-based — no data sent to any server
When to Use This Tool
- Hiding spoilers in forum posts, emails, or online discussions
- Concealing puzzle answers or riddle solutions
- Obfuscating text for fun, games, or geocaching clues
- Learning about basic substitution ciphers and cryptography fundamentals
- Decoding ROT13-encoded text you encounter online
Technical Details
The algorithm iterates through each character. For uppercase letters (A–Z, code points 65–90) and lowercase letters (a–z, code points 97–122), it adds 13 and wraps around using modular arithmetic. All other characters are passed through unchanged. Because ROT13(ROT13(x)) = x, the same function serves for both encoding and decoding. ROT13 provides no cryptographic security — it is trivially reversible. For an actual cipher, try the Caesar Cipher with a custom shift value, or use proper encryption tools for sensitive data.
Conclusion
ROT13 is the internet's classic way to hide spoilers and puzzle answers in plain sight. This free, browser-based tool encodes and decodes instantly — just paste, click, and copy. No installation, no sign-up, and your text stays entirely on your device.