ROT13 Encoder / Decoder
Encode or decode ROT13 - and any Caesar shift from 1 to 25 - instantly and entirely in your browser.
ROT13 & Caesar cipher
Rotates letters through the alphabet. With the default shift of 13, encoding and decoding are the same operation - apply it twice and you are back to the original.
About ROT13 Encoder / Decoder
ROT13, short for "rotate by 13," is a Caesar cipher that shifts each letter 13 places through the 26-letter alphabet, so A becomes N and N becomes A. Because 13 is exactly half of 26, applying the shift twice returns the original text, which means the same operation both encodes and decodes ROT13.
Only the 26 basic Latin letters are rotated, and letter case is preserved. Digits, spaces, punctuation and every other character pass through unchanged. That property makes ROT13 handy for lightly obscuring text - spoilers, punchlines, quiz answers - without disguising its overall shape or length.
A shift slider lets you pick any rotation from 1 to 25, turning the tool into a general Caesar cipher. For the default shift of 13 the encoded and decoded outputs are identical; for any other shift they differ, so the tool shows both the forward-shifted result and the backward-shifted result you use to decode.
ROT13 provides no security whatsoever - it has no key and is trivially reversible, so it should never be used to protect sensitive data. Everything runs client-side: your text is transformed in the browser and never sent to a server.
How to use it
- 1Type or paste your text into the text box.
- 2Leave the shift at 13 for classic ROT13, or drag the slider to any value from 1 to 25 for a different Caesar shift.
- 3Read the shifted-forward output; to decode a message, use the shifted-back result, which is identical to the forward output when the shift is 13.
- 4Copy whichever result you need - nothing is uploaded, so you can safely use it on private text.
Common use cases
- -Hiding spoilers, punchlines, or puzzle answers in forums and chat so readers reveal them deliberately
- -Teaching or demonstrating how the Caesar cipher and modular alphabet rotation work
- -Solving or creating ROT13 and Caesar-shift puzzles in CTFs and escape rooms
- -Lightly obscuring text such as email addresses in a way that is easy to reverse
- -Quickly decoding ROT13 content you come across online without installing anything
Frequently asked questions
- How do I decode ROT13 text?
- Apply ROT13 again. Because a 13-place shift is exactly half of the 26-letter alphabet, the same rotation both encodes and decodes, so passing ROT13 text through the tool a second time restores the original.
- Is ROT13 secure encryption?
- No. ROT13 is a simple letter-substitution cipher with no key and is trivially reversible, so it offers no real security. Use it only to obscure text casually, never to protect passwords or sensitive information.
- What is a Caesar cipher?
- A Caesar cipher shifts every letter a fixed number of positions through the alphabet. ROT13 is the special case with a shift of 13, and this tool supports any shift from 1 to 25.
- Does ROT13 change numbers or punctuation?
- No. Only the 26 Latin letters A-Z are rotated, and letter case is preserved. Digits, spaces, punctuation and other symbols pass through unchanged.
- Is my text sent to a server?
- No. The encoding and decoding run entirely in your browser using client-side JavaScript, so the text you enter never leaves your device.
- Why do encoding and decoding differ for shifts other than 13?
- Only a shift of 13 is self-inverse, because 13 plus 13 equals a full loop of 26. For any other shift you must rotate forward to encode and backward by the same amount to decode, which is why the tool shows both results.