Encode or decode a Caesar cipher
Encode or decode text with a classic Caesar shift cipher at any offset, including the ROT13 preset.
Encode shifts letters forward, Decode shifts them back by the same amount.
Choose any shift from 1 to 25, or use the ROT13 button for the classic 13-shift preset.
The result updates instantly as you type or adjust the shift.
Frequently asked
What is a Caesar cipher?
It's one of the oldest known encryption methods: every letter in the message is shifted a fixed number of places through the alphabet. A shift of 3 turns "A" into "D", for example.
What is ROT13?
ROT13 is a Caesar cipher with a shift of exactly 13. Because the alphabet has 26 letters, applying ROT13 twice returns the original text, which makes it a popular way to lightly obscure text like puzzle spoilers.
Is this secure encryption?
No. A Caesar cipher is trivial to break, since there are only 25 possible shifts to try. It's meant for puzzles, learning, and light obfuscation, not for protecting sensitive information.
Does it preserve capitalization and punctuation?
Yes, only letters A-Z and a-z are shifted. Numbers, spaces, and punctuation are left untouched, and case is preserved.