Encode and decode text with any Caesar shift in one click
Tip
ROT-13 (shift = 13) is self-inverse — encoding and decoding use the same operation. Numbers and punctuation are left unchanged; only A–Z and a–z are shifted.
The Caesar cipher is one of the oldest and simplest encryption techniques, shifting each letter in your message by a fixed number of positions in the alphabet. Use this free online Caesar cipher encoder and decoder to encrypt plain text or crack ciphered messages instantly. Adjust the shift from 1 to 25 — including the popular ROT-13 variant — and copy results in one click.
A Caesar cipher is a substitution cipher where each letter in the text is shifted a fixed number of positions along the alphabet. For example, with a shift of 3, 'A' becomes 'D' and 'Z' becomes 'C'. It was famously used by Julius Caesar for private correspondence.
To decode, select Decode mode and enter the same shift that was used to encode the message. If you don't know the shift, you can try all 25 values — this tool makes it quick to test each one. With a shift of 13 (ROT-13), encoding and decoding are the same operation.
ROT-13 is a special case of the Caesar cipher with a shift of exactly 13. Because there are 26 letters in the alphabet, applying ROT-13 twice returns the original text — so the same button encodes and decodes. It is commonly used to obscure spoilers or puzzle answers online.
Only the 26 letters of the English alphabet (A–Z, a–z) are shifted. Numbers, spaces, and all punctuation marks pass through unchanged, preserving the original formatting and readability of your text.