Caesar / ROT13 Cipher
Shift letters by any amount, with a brute-force table.
โROT13 (shift 13) is its own inverse โ decode twice to get the original.
About the Caesar / ROT13 Cipher
Shift every letter of your message by any amount from 0 to 25 to encode or decode a Caesar cipher. A slider picks the shift with live ROT labels, a decode switch reverses the direction, and a brute-force table shows all 26 shifts at once for cracking unknown keys.
How to use the Caesar / ROT13 Cipher
- Type your text into the input field.
- Drag the Shift slider to choose an offset โ 13 gives classic ROT13.
- Tick Decode (reverse shift) when recovering the original from ciphertext.
- Tick Show all 26 shifts to scan every possible decoding in a table.
- Copy the result from the Result box.
Caesar / ROT13 Cipher FAQ
What makes ROT13 special?
Shifting by 13 is its own inverse because 13 doubled equals 26, the size of the alphabet, so applying ROT13 twice returns the original text.
How do I decode a message with an unknown shift?
Enable Show all 26 shifts and read down the table until a line makes sense; the row label tells you which ROT value was used.
Are digits and punctuation shifted?
No. Only letters A to Z move; numbers, spaces and symbols pass through untouched, which matches the classical Caesar definition.