tools / rot13
rot13/
ROT13, ROT47 and the Caesar cipher. ROT13 / ROT47 undo themselves when applied again; the Caesar cipher lets you pick the shift and direction.
Input
Result
FAQ
Is ROT13 encryption, and can I use it to keep something secret?
No. ROT13 just replaces each letter with the one 13 places away in the alphabet. There is no key, so anyone can undo it. It is meant for hiding spoilers, answers and puzzle solutions so readers don't see them by accident. The Caesar cipher is the same: there are only 25 possible shifts, and trying them all breaks it. For real secrecy, use proper encryption such as AES.
Why does applying ROT13 twice give the original text back?
The alphabet has 26 letters and 13 is exactly half, so A becomes N and N becomes A again. The same operation both encrypts and decrypts. ROT47 works the same way: there are 94 printable ASCII characters and 47 is half of them. That is why these two modes have no encrypt / decrypt direction; only the Caesar shift needs one.
What is the difference between ROT13, ROT47 and the Caesar cipher?
ROT13 is a Caesar cipher with the shift fixed at 13, and it only changes English letters. ROT47 works on the 94 visible characters from ASCII 33 to 126, so letters, digits and punctuation all change. The Caesar shift lets you pick any shift from 1 to 25 and also only changes letters. For example, “Hello, World!” becomes “Uryyb, Jbeyq!” with ROT13 and “w6==@[ (@C=5P” with ROT47.
How do I decrypt a Caesar cipher, and what if I don't know the shift?
Choose “Caesar shift”, set the direction to “Decrypt”, and enter the number that was used to encrypt: text encrypted with shift 3 is decrypted with shift 3. This tool doesn't guess the shift or list every result at once. If you don't know the shift, try 1 to 25 one by one and see which result reads like normal words.
What happens to digits, spaces, Chinese characters and punctuation?
ROT13 and the Caesar shift only change A to Z and a to z. Case is kept, and digits, spaces, punctuation, Chinese characters and accented letters (such as é) are left as they are. ROT47 changes every visible character from ASCII 33 to 126, including digits and punctuation, while spaces, line breaks, Chinese characters and non-ASCII letters stay as they are.
What does “⇄ Use result as input” do?
It puts the contents of the result box back into the input box. Applying ROT13 or ROT47 again gives the original text, so after one click the result box shows what you started with. In Caesar shift mode it also swaps encrypt and decrypt, so the output goes back to the original text too. If the result box is empty, nothing happens except a message saying there is no result to use as input.
What happens if I enter a shift of 0, 26 or a decimal?
The shift must be a whole number from 1 to 25. Anything else (empty, 0, 26, a negative number or one with a decimal part such as 3.5) clears the result and shows a message asking for a whole number from 1 to 25. Shifts of 0 and 26 leave the text unchanged, so they are not allowed. To move back n places, choose “Decrypt” with n, or “Encrypt” with 26 minus n.
Is my input uploaded?
No. The conversion happens in your browser and nothing is sent to a server.