ROT13 Encoder / Decoder

How to use

1. Enter Text — Type or paste the text you want to encode or decode.
2. Choose Shift — Select a Caesar cipher shift. ROT13 uses a shift of 13 (default).
3. Read Output — The result appears instantly. ROT13 is symmetric — applying it twice returns the original text.

Free ROT13 Encoder & Decoder

Encode and decode text with the ROT13 Caesar cipher. Choose any shift value from 1 to 25. All processing happens locally in your browser for complete privacy.

Common Uses

• Hide puzzle answers or quiz solutions
• Obfuscate spoilers in forums and comments
• Teach basic cryptography concepts
• Quickly encode casual messages
• Experiment with Caesar cipher variations

How It Works

Each letter in the input is shifted forward by the chosen number of positions in the alphabet. Wrapping occurs at Z back to A. Because ROT13 uses a shift of exactly half the alphabet (13 of 26), encoding and decoding are the same operation.

Privacy

No text is transmitted. The entire cipher runs in your browser.

Related: Vigenere Cipher, Base64 Encoder/Decoder, JavaScript Escape/Unescape.

Frequently asked questions

What is ROT13?

ROT13 (rotate by 13 places) is a simple Caesar cipher that replaces each letter with the 13th letter after it in the alphabet. Because the alphabet has 26 letters, applying ROT13 twice returns the original text.

Is ROT13 secure?

No. ROT13 offers no real security — it is trivial to reverse. It is mainly used for obfuscation (e.g., hiding puzzle answers or spoilers) and educational purposes.

Can I use a different shift?

Yes. The tool supports any Caesar shift from 1 to 25, so you can experiment with ROT5, ROT7, or any other value.

Does it handle non-alphabetic characters?

Yes. Numbers, spaces, punctuation, and Unicode characters are left unchanged. Only A-Z and a-z are shifted.

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