ROT13 Cipher - Encode & Decode Text Instantly

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. For example, 'A' becomes 'N', 'B' becomes 'O', and so on. When you reach the end of the alphabet, it wraps around - 'N' becomes 'A', 'O' becomes 'B', etc.

ROT13 is not secure encryption and should never be used for protecting sensitive information. It's a simple substitution cipher that can be easily broken by anyone who knows the pattern. ROT13 is designed for obfuscation, not security - it's meant to hide text from casual viewing, not from determined attackers.

ROT13 has several practical applications despite its simplicity:

• Hiding spoilers in online discussions and forums
• Obscuring potentially offensive content that readers can choose to decode
• Creating simple puzzles and educational exercises
• Preventing accidental reading of text (like puzzle solutions)
• Demonstrating basic cryptographic principles in educational settings

ROT13 only affects alphabetic characters (A-Z and a-z). Other characters remain unchanged:

• Letters (A-Z, a-z) are rotated 13 positions
• Numbers (0-9) remain the same
• Punctuation marks (.,!?;:) stay unchanged
• Special characters (@#$%^&*) are preserved
• Spaces and line breaks remain intact
• Case is preserved (uppercase stays uppercase, lowercase stays lowercase)

Yes, all text processing happens directly in your browser using JavaScript. Your input text never leaves your device or gets transmitted to any servers. This ensures complete privacy and security when working with any content while also providing instant results without server delays.

ROT13 became popular in early internet culture, particularly on Usenet newsgroups in the 1980s and 1990s. It was commonly used to hide spoilers, offensive jokes, and puzzle solutions in text-based online discussions.

The cipher is based on the Caesar cipher, attributed to Julius Caesar, but uses a rotation of 13 instead of 3. The choice of 13 is particularly elegant because the English alphabet has 26 letters, making ROT13 its own inverse - applying it twice returns the original text.