Caesar Cipher Encoder and Decoder

Every letter is shifted forward through the alphabet by a fixed number of places, and the alphabet wraps around so that shifting Z by one gives A. With a shift of 3, A becomes D, B becomes E, and so on. To decode, you shift by the same amount in the opposite direction, which is the same as shifting forward by 26 minus the key.

Only the letters A to Z and a to z are shifted, and their case is preserved. Spaces, digits, punctuation, line breaks and accented or non-English characters pass through unchanged, so the shape of your message stays the same.

ROT13 is just the Caesar cipher with a shift of 13. Because 13 is exactly half of 26, applying ROT13 twice returns the original text, so the same operation both encodes and decodes. Set the shift to 13 here to use ROT13.

There are only 25 possible shifts, so you can simply try them all. Open the brute-force table to see every shift from 1 to 25 at once, then pick the line that reads as plain text. This is why the Caesar cipher offers no real security.

No. The Caesar cipher is a classical cipher meant for puzzles, history and learning, not for protecting secrets. With only 25 possible keys it can be broken instantly by trying every shift, and it falls to simple frequency analysis. For real protection use a tool that applies modern, password-based encryption such as AES.

Yes. The encoding and decoding run entirely in your browser. Your text is never uploaded to a server and nothing is stored.