Caesar Cipher Encoder & Decoder
Encrypt and decrypt text with a Caesar shift — or brute-force all 26.
The Caesar cipher shifts each letter by a fixed amount. To decrypt a message, use the same shift on the "Decoded" side — or, if you don't know the shift, tick "Show all 26 shifts" and look for the readable line. Letters only; spaces and punctuation are kept. Runs in your browser.
Encode and decode text with the classic Caesar cipher, which shifts each letter by a fixed amount. Drag the shift slider to see the encrypted and decrypted text update live. Don't know the key? Tick 'Show all 26 shifts' to brute-force a message and spot the readable line. Letters are shifted; spaces, numbers and punctuation pass through unchanged. A great intro to cryptography. Runs in your browser.
How to use the Caesar Cipher
- Type the message you want to encrypt or decrypt.
- Set the shift amount with the slider.
- Read the encoded and decoded text, or brute-force all 26 shifts.
Frequently asked questions
How do I decode a Caesar cipher without the key?
Tick 'Show all 26 shifts'. The tool lists every possible decoding; the one that reads as plain language is the answer — there are only 25 real shifts to scan.
Is the Caesar cipher secure?
No. With only 25 possible keys it's trivial to brute-force, so it's used for puzzles and teaching, not real security. For that, use modern encryption.
What happens to numbers and punctuation?
Only letters A–Z and a–z are shifted; digits, spaces and punctuation are left exactly as they are, and letter case is preserved.