ROT13 Encoder / Decoder
Encode or decode text with ROT13, the fixed-shift-13 Caesar cipher. ROT13 is its own inverse, so the same action encodes and decodes; non-letters pass through unchanged.
Input
Output
ROT13 is symmetric — apply it again to decode.
Guides
ROT13 ("rotate by 13 places") is a simple letter-substitution cipher that replaces every letter with the one 13 positions after it in the alphabet. Paste any text into this tool and it instantly returns the ROT13-transformed version. Because the tool runs entirely in your browser, nothing you type is ever uploaded or stored.
How ROT13 works
The English alphabet has 26 letters, and 13 is exactly half of that. Shifting a letter forward by 13 and then forward by 13 again lands you back where you started — so ROT13 is its own inverse. A becomes N, and applying the shift to N returns A. This means there is no separate "decode" mode: encoding and decoding are the same operation. Run any text through the tool once to scramble it, and run the scrambled text through again to recover the original.
Only the 26 basic Latin letters are rotated. Case is preserved (uppercase stays uppercase, lowercase stays lowercase), and everything else — digits, spaces, punctuation, emoji, accented characters — passes through unchanged. So Hello, World! 42 becomes Uryyb, Jbeyq! 42.
ROT13 is a special case of the Caesar cipher, the classic shift cipher named after Julius Caesar. A general Caesar cipher can use any shift from 1 to 25; ROT13 simply fixes the shift at 13. If you need a different shift amount, use the Caesar Cipher tool instead.
Common uses
ROT13's purpose has never been secrecy — it is trivially reversible by anyone. Instead it is used to lightly obscure text so that it is not readable at a glance:
- Spoiler and punchline masking. Forum and Usenet posters have long used ROT13 to hide movie spoilers, puzzle answers, or joke punchlines. Readers who want the answer copy the garbled text and decode it deliberately; everyone else skims past without accidentally reading it.
- Hiding offensive or plot-critical text in the middle of otherwise plain messages.
- Programming puzzles and teaching. ROT13 is a favorite first exercise for learning string manipulation, and it appears in coding challenges and CTF warmups.
ROT13 is not encryption
Do not use ROT13 to protect anything that actually matters — passwords, personal data, private messages, or API keys. It provides zero cryptographic security: there is no key, the transformation is public and fixed, and reversing it takes no effort. For real protection, use a proper encryption tool with a secret key.
Is ROT13 the same as ROT47?
No. ROT13 rotates only the 26 alphabet letters. ROT47 works over a larger set of 94 printable ASCII characters, so it also scrambles digits and punctuation. This tool implements classic ROT13.
Why does my text look unchanged?
If your input contains no A–Z letters (only numbers, symbols, or non-Latin scripts), there is nothing for ROT13 to rotate, so the output matches the input exactly.