Caesar Cipher Encoder/Decoder
Encode and decode text using the classic Caesar cipher (shift cipher). Includes ROT13 and brute-force decoder.
100% client-side processing
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Encode and decode text using the classic Caesar cipher (shift cipher). Includes ROT13 and brute-force decoder.
100% client-side processing
Caesar Cipher Tool encodes and decodes text using the classic shift cipher — pick a shift, type your message, and watch every letter slide down the alphabet. It includes a ROT13 quick toggle and a brute-force mode that tries all 25 shifts at once. Perfect for puzzle hunters, CTF players, teachers, and anyone curious about how cryptography began.
Named after Julius Caesar, who used a shift of three to protect military correspondence, this is one of the oldest encryption methods on record — the Roman historian Suetonius described it nearly two thousand years ago. The idea is simple: replace each letter with the one N positions later in the alphabet, wrapping from Z back to A.
Its weakness is equally simple. With only 25 possible keys, an attacker can just try them all, and frequency analysis — in English, E is by far the most common letter — breaks it even faster. That is why the Caesar cipher today lives in puzzle hunts, geocaching logs, online forums that use ROT13 to hide spoilers, and classrooms. It remains the perfect first lesson in both encryption and the reason real security needs mathematically hard problems rather than secret recipes.
A substitution cipher where each letter is shifted by N positions in the alphabet.
No, it's easily broken with brute force. It's used for educational purposes.
ROT13 is a Caesar cipher with a fixed shift of 13. Applying it twice returns the original text, since 13 + 13 = 26.