ROT13 is a simple letter substitution cipher where each letter is replaced by the letter 13 positions after it in the alphabet.

No, ROT13 is not secure for sensitive data. It's used for entertainment, protection from accidental spoilers, and educational purposes.

13 is half of 26 (letters in the alphabet), making ROT13 symmetric - applying it twice returns the original text.

What are common ROT13 uses?

Spoiler hiding in forums, simple text obfuscation, puzzle games, training for codebreaking, and simple fun encoding.

How do I decode ROT13?

ROT13 is reciprocal - apply the same transformation again to decode. Running it twice returns the original text.

Does it affect numbers and symbols?

No, ROT13 only transforms letters. Numbers, punctuation, and special characters remain unchanged.

ROT13 Encoder/Decoder

Transform text using the reversible ROT13 cipher - same tool encodes and decodes

Reversible

Apply twice to return to original text

Instant Transform

One-click encoding and decoding

13-Position Shift

Exact middle of 26-letter alphabet

Obfuscation Only

For spoilers and fun, not security

Enter Text 0 characters

About ROT13

ROT13 is a 13-letter shift of the Caesar cipher. It's symmetric - applying it twice returns the original text.

Quick Facts

Numbers unchanged
Symbols preserved
Case maintained
Bijective function

How ROT13 Works

The Mapping

Each letter shifts exactly 13 positions:

A↔N, B↔O, C↔P, D↔Q

E↔R, F↔S, G↔T, H↔U

I↔V, J↔W, K↔X, L↔Y

M↔Z

Why 13? It's exactly half of 26, making ROT13 symmetric (A→N, N→A)

Key Properties

Symmetric: Encrypting and decrypting use the same operation
Involutory: f(f(x)) = x (applying twice returns original)
Preserving: Non-alphabetic characters unchanged
Case-aware: Maintains uppercase/lowercase
Cipher type: Substitution cipher (subset of Caesar)
Usage: Text obfuscation, spoiler hiding, fun encoding

Common Applications

Spoiler Hiding

Obfuscate movie/book spoilers in forums and comments

Puzzle Games

Create simple encoding challenges and riddles

Learning Tool

Understand cipher concepts and substitution basics

Casual Fun

Funny obfuscation for non-sensitive content

Important Notes

No Security: ROT13 is completely trivial to break
Obfuscation Only: Use for hiding spoilers, not secrets
Breakable: Can be solved by hand or script in seconds
Learning Only: Great for understanding cipher concepts

Real Security: Use AES, RSA, TLS for actual protection
Fun Encoding: Perfect for puzzles and games
Symmetric Key: Both parties need to know it's ROT13
Historic: One of the oldest known cipher methods

Keyboard Shortcuts

Ctrl + Enter Transform Text

Ctrl + Shift + C Copy Result

Ctrl + L Clear All