ROT13 Encoder / Decoder
Encode & decode ROT13
ROT13 is symmetric: applying it again to the result restores the original text.
What Is This Tool?
ROT13 ("rotate by 13") is a simple letter-substitution cipher that shifts each ASCII letter 13 places through the alphabet, wrapping around from Z back to A. Because the alphabet has 26 letters, applying ROT13 twice returns the original text, so the same "Apply ROT13" action both encodes and decodes. Digits, punctuation, and other characters are left unchanged.
How to Use
Type or paste text into the field.
Click Apply ROT13 to transform it in place.
Click Apply ROT13 again on the result to get your original text back.
Copy the result with the Copy button.
Features
- Same button both encodes and decodes (ROT13 is its own inverse)
- Only ASCII letters A-Z / a-z are rotated; everything else is untouched
- Preserves letter case
- Instant, in-place transformation
- 100% client-side — nothing leaves your browser
Examples
Input: Hello, World!
ROT13: Uryyb, Jbeyq!
Common Use Cases
- Obscuring spoilers, puzzle answers, or joke punchlines in forum posts
- Quick, reversible text scrambling for programming exercises
- Decoding ROT13-encoded messages found online
- Demonstrating basic substitution ciphers for teaching purposes
Frequently Asked Questions
Is ROT13 secure encryption?
No. ROT13 provides no real security — it's a simple, well-known letter substitution used for obscuring text (like spoilers), not for protecting sensitive information.
Why is there only one button?
ROT13 is symmetric: shifting by 13 twice returns you to the original 26-letter alphabet position, so the exact same operation both encodes and decodes text.
What happens to numbers and punctuation?
They're left completely unchanged. Only ASCII letters A-Z and a-z are rotated; digits, spaces, and symbols pass through as-is.
Does it preserve uppercase and lowercase?
Yes, uppercase letters rotate to uppercase letters and lowercase letters rotate to lowercase letters, so the original casing pattern is preserved.
Does it work with accented or non-English letters?
No, only the standard ASCII A-Z/a-z range is rotated. Accented letters and non-Latin scripts are left unchanged since they fall outside the 26-letter ROT13 alphabet.
Is my text uploaded anywhere?
No, the rotation happens entirely locally in your browser with simple character-code arithmetic. Nothing is sent to a server.