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ROT13 Cipher

Encode and decode text using the ROT13 Caesar cipher

■ 01

What is ROT13?

ROT13 (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 there are 26 letters, applying ROT13 twice returns the original t…

■ 02

How does it work?

Using This Tool Enter any text in the input field and click Convert. The same operation both encodes and decodes text. Non-alphabetic characters (numbers, punctuation, spaces) remain unchanged. Use Cases ROT13 is common…

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Sample Cases

Covers Simple text, With numbers and symbols, and Double conversion returns original so you can compare common inputs and outputs quickly.

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Source code from the selected tool, shown here alongside the live version on the right.

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TypeScript

typescript

// ROT13 cipher - self-inverse encryption/decryption
function rot13(text: string): string {
  return text.replace(/[a-zA-Z]/g, (char) => {
    const start = char <= 'Z' ? 65 : 97;
    return String.fromCharCode(
      ((char.charCodeAt(0) - start + 13) % 26) + start
    );
  });
}