🔐 Caesar Cipher
Encrypt and decrypt text using the Caesar cipher. Shift letters by any number of positions.
About the Caesar Cipher
The Caesar cipher is one of the oldest known encryption methods, named after Julius Caesar who used it for private correspondence. Each letter in the plaintext is shifted forward by a fixed number of positions in the alphabet. This tool runs entirely in your browser — nothing is uploaded.
How it works
- Encrypt — Each letter is shifted forward by the chosen number. With shift 3, A becomes D, B becomes E, etc.
- Decrypt — Each letter is shifted backward by the chosen number, reversing the encryption.
- Letter case is preserved; non-letter characters (digits, punctuation, spaces) are left unchanged.
- The shift wraps around the alphabet, so Z shifted by 1 becomes A.
Use cases
- Learning the basics of cryptography and substitution ciphers.
- Creating simple puzzles, escape-room clues, or scavenger hunts.
- Obfuscating spoiler text or mild spoilers in casual chat.
- Demonstrating why classical ciphers are insecure for real secrets.
Frequently asked questions
Is the Caesar cipher secure? No. With only 25 possible shifts, it is trivially broken by brute force or frequency analysis. Use it for fun and learning, not for protecting sensitive data.
Does this tool upload my text? No. All encryption and decryption happens locally in your browser.
What shift should I use? Any value from 1 to 25 works. The classic Caesar cipher uses shift 3. ROT13 uses shift 13.
Can I encrypt non-English text? Only the 26 letters A-Z are shifted. Characters in other scripts pass through unchanged.