Caesar cipher translator

Type on the left, read the shifted text on the right. Swap the boxes to decode, and set Shift to any number from 1 to 25.

If the shift is a mystery, leave the tool on any setting and look at the panel below. Every shift is listed and ranked by how much the result reads like English, so the answer is usually the top row.

Pick a number and move every letter that far along the alphabet, wrapping from Z back to A. At a shift of three, A becomes D and dawn becomes gdzq. Decoding runs the same distance backwards.

Only letters move. Digits, spaces and punctuation stay exactly where they were, which keeps the shape of the message and makes it easy to spot word lengths. That is also the weakness: a three-letter word at the start of a sentence is probably "the".

Suetonius describes Julius Caesar shifting letters by three in his private correspondence, which is where the name comes from. He adds that Augustus preferred a shift of one, and left Z alone rather than wrapping it round.

The idea survived into the 20th century as a toy. Radio serials in the 1930s and 1940s posted decoder badges to listeners, and the Captain Midnight Code-O-Graph was a Caesar wheel on a pin: line up the letters, read the secret message at the end of the episode, and find out you had been told to drink your Ovaltine.

ROT13 is this cipher with the shift welded to 13, the setting that makes it undo itself. Atbash mirrors the alphabet instead of rotating it.

If the message has digits and symbols in it, a cipher is the wrong guess. Try the cipher identifier, which checks the encodings too.