ROT13 Encoder & Decoder
Instantly encode or decode ROT13 text. This self-inverse cipher is used for geocaching hints, online spoiler protection, and simple text obfuscation.
Self-inverse property: ROT13 is its own inverse—applying it twice returns the original text. This makes it perfect for hiding spoilers since the same tool both encodes and decodes.
What is ROT13?
ROT13 (short for "rotate by 13 places") is a simple letter substitution cipher that replaces each letter with the letter 13 positions after it in the alphabet. Since the English alphabet has 26 letters, applying ROT13 twice returns the original text, making it a self-inverse cipher.
ROT13 is a special case of the Caesar cipher with a fixed shift of 13. While it provides no real cryptographic security, its simplicity and self-inverse property make it ideal for hiding spoilers, hints, and puzzle answers.
How ROT13 Works
The ROT13 transformation is straightforward:
- A becomes N, B becomes O, C becomes P, and so on
- N becomes A, O becomes B, P becomes C, wrapping around
- Numbers, spaces, and punctuation remain unchanged
- Case is preserved (uppercase stays uppercase, lowercase stays lowercase)
ROT13 Alphabet Mapping
The complete letter substitution table:
- Plain: A B C D E F G H I J K L M
- ROT13: N O P Q R S T U V W X Y Z
- Plain: N O P Q R S T U V W X Y Z
- ROT13: A B C D E F G H I J K L M
Notice that each pair of letters (A↔N, B↔O, etc.) swaps with each other, which is why applying ROT13 twice restores the original text.
ROT13 in Geocaching
Geocaching.com uses ROT13 for all cache hints. When a cache owner provides a hint, the system automatically encodes it with ROT13. This allows seekers to choose whether to view the hint or solve the puzzle without help.
Decoding Geocaching Hints
When you see a hint like "Ybbx haqre gur ebpx", simply paste it into this decoder to reveal "Look under the rock". The geocaching website has a built-in decoder, but our tool is faster and works offline.
Common Geocaching ROT13 Uses
- Cache hints: Physical hiding spot clues
- Forum spoilers: Puzzle solutions in discussion threads
- Puzzle cache answers: Checking solutions without revealing them
- Travel bug hints: Clues for trackable items
The Self-Inverse Property
ROT13's most useful feature is being self-inverse—the same operation that encodes also decodes. Mathematically, this works because 13 + 13 = 26 (the alphabet length), so two rotations of 13 equals a full rotation back to the start.
This property means:
- You don't need separate encode/decode buttons
- Anyone can decode simply by re-encoding
- No keys or passwords to remember
ROT13 Examples
Example 1: Simple Text
- Original: HELLO
- ROT13: URYYB
Example 2: Geocaching Hint
- Encoded: Oruvaq gur gerr fghzc
- Decoded: Behind the tree stump
Example 3: Mixed Content
- Original: Meet at N 47° 30.000'
- ROT13: Zrrg ng N 47° 30.000'
Notice that numbers, symbols, and coordinates remain unchanged.
Why ROT13 Isn't Encryption
While ROT13 transforms text, it's not secure encryption:
- The algorithm is publicly known and trivial to reverse
- There's no key or password involved
- Any ROT13 decoder instantly reveals the content
- It's meant for obfuscation, not security
ROT13 is useful for preventing accidental spoilers—you won't accidentally read a ROT13 hint while scrolling past—but it won't protect sensitive information.
ROT13 vs Other Ciphers
ROT13 vs Caesar Cipher
ROT13 is a Caesar cipher with shift=13. The Caesar cipher allows any shift from 1-25, while ROT13 is fixed. Other shifts (like ROT1 or ROT3) don't have the self-inverse property and require separate encoding and decoding operations.
ROT13 vs Atbash
Like ROT13, Atbash is self-inverse. However, Atbash reverses the alphabet (A↔Z, B↔Y) rather than rotating it. Both are used in geocaching puzzles and produce different results for the same input.
ROT13 vs Vigenère
The Vigenère cipher uses a keyword to apply varying Caesar shifts, making it much harder to break. ROT13's single fixed shift makes it trivial to decode, while Vigenère requires knowing (or cracking) the keyword.
History of ROT13
ROT13 emerged in the early 1980s on Usenet newsgroups as a way to hide spoilers, punchlines, and offensive content. Users could choose to decode messages they wanted to see while scrolling past encoded content they didn't.
The convention spread throughout internet culture and was adopted by geocaching.com when the platform launched in 2000. Today, ROT13 remains the standard for geocaching hints worldwide.
Tips for Using ROT13
- Verify your result: If the output doesn't look like readable text, the input might use a different cipher
- Watch for double-encoding: Applying ROT13 to already-ROT13 text returns the original—the decoder becomes an encoder
- Numbers are clues: If numbers in your decoded text seem random, they might be coordinates or part of a secondary puzzle
- Try other ciphers: If ROT13 doesn't produce readable text, the cache owner might have used a different Caesar shift or cipher type
Related Cipher Tools
If ROT13 doesn't decode your text, try these related tools:
- Caesar Cipher: Try all 26 rotations with brute force to find the correct shift value.
- Atbash Cipher: Another self-inverse cipher that reverses the alphabet instead of rotating it.
- Vigenère Cipher: For keyword-based polyalphabetic ciphers often found in more complex puzzle caches.