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ROT13 Cipher

ROT13 Cipher

Encode and decode text with ROT13, a fixed Caesar cipher that rotates Latin letters by 13 positions. Commonly used for spoiler text, puzzle messages, and light obfuscation.

Input
0 chars · 0 bytes
Try:
Result
✓ Fixed Caesar shift by 13 letters ✓ No key or settings required ✓ We never store your messages ✓ Processed on our server
Examples
Encode HELLO
Input HELLO WORLD
Output URYYB JBEYQ

ROT13 rotates every Latin letter by 13 positions while preserving spaces and punctuation.

Decode ROT13 text
Input URYYB JBEYQ
Output HELLO WORLD

Applying the same ROT13 transformation restores the original message.

Encode spoiler text
Input THE VILLAIN WINS
Output GUR IVYYNVA JVAF

ROT13 is commonly used to hide spoilers while still allowing readers to decode them easily.

Encode a puzzle hint
Input LOOK UNDER THE TABLE
Output YBBX HAQRE GUR GNOYR

Puzzle creators sometimes use ROT13 to conceal hints without requiring a secret key.

How ROT13 works

ROT13 is a special version of the Caesar cipher that always shifts Latin letters by exactly 13 positions. A becomes N, B becomes O, C becomes P, and so on. After M, the alphabet wraps around back to A.

Because the English alphabet contains 26 letters and 13 is exactly half of that, applying ROT13 twice restores the original message. This means the same operation is used for both encoding and decoding.

ROT13 changes only Latin letters. Numbers, spaces, punctuation marks, and most symbols remain unchanged.

ROT13 example

The transformation is easy to visualize because every letter maps to the letter exactly 13 positions away — and the mapping is its own inverse:

ABCDEFGHIJKLM
↕↕↕↕↕↕↕↕↕↕↕↕↕
NOPQRSTUVWXYZ

For example, HELLO WORLD becomes URYYB JBEYQ. Applying ROT13 again restores the original text.

ROT13 and security

ROT13 is not considered encryption by modern standards. There is no secret key, and anyone familiar with the method can reverse it instantly.

Its purpose is light obfuscation rather than protection. It is often used to hide spoilers, puzzle answers, jokes, or content that should not be immediately visible without a deliberate action.

ROT13 vs Caesar cipher

ROT13 is effectively a Caesar cipher with a fixed shift of 13. Unlike a normal Caesar cipher, there is no configurable key or shift value.

This simplicity makes ROT13 easy to use and recognize, but also makes it unsuitable for any situation that requires real confidentiality.

FAQ

No. ROT13 is a simple obfuscation technique, not secure encryption. It uses no secret key and can be reversed immediately.

The Latin alphabet contains 26 letters. A shift of 13 moves each letter exactly halfway around the alphabet, making the transformation self-reversing.

Every letter is shifted 13 positions. Applying the same shift again moves it another 13 positions, completing a full 26-letter cycle and returning to the starting letter.

No transformation is applied to numbers, spaces, punctuation marks, or most symbols. Only Latin letters are rotated.

ROT13 is often used for spoiler text, puzzle hints, internet jokes, and situations where content should be hidden casually without real security.

ROT13 is a specific Caesar cipher variant that always uses a shift of 13. A traditional Caesar cipher may use many different shift values.
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