Caesar Cipher
Shift letters by a custom amount to encode or decode. Non-letter characters are preserved.
100% client-side · no upload
What is the Caesar cipher?
The Caesar cipher is a substitution cipher where each letter in the plaintext is shifted by a fixed number of positions in the alphabet. With a shift of 3 (the shift Julius Caesar reportedly used), A becomes D, B becomes E, …, W becomes Z, X becomes A, Y becomes B, Z becomes C. To decode, shift back by the same amount (or use the Decode button, which applies the inverse shift automatically).
How to use
- Set the shift amount (1–25) in the number input.
- Paste your text in the input box.
- Click Encode to encrypt or Decode to decrypt.
Related tools: ROT13, Atbash Cipher, Morse Code
Preguntas frecuentes
- What is the Caesar cipher?
- The Caesar cipher shifts each letter in the alphabet by a fixed number of positions. With a shift of 3, A becomes D, B becomes E, etc. It is one of the oldest known encryption techniques, used by Julius Caesar in his private correspondence.
- Does my data leave my device?
- No. The Caesar cipher transformation is pure JavaScript running entirely in your browser.
- Does it work on mobile?
- Yes. The tool works in any modern mobile browser and the output updates instantly as you adjust the shift.