Caesar Cipher
Each letter of the plaintext is replaced by the letter a fixed number of positions further down the alphabet. Tweak the shift and watch the alphabets re-align.
Per-character mapping
Hover or scan: each tile shows where one input letter lands. Non-letters pass through unchanged.
How it works
The Caesar cipher is a monoalphabetic substitution cipher.
For shift k, every plaintext letter p
(numbered 0–25) becomes
c = (p + k) mod 26. Decryption is the same operation
with -k.
Because there are only 26 possible keys, the cipher is trivially broken by brute force — but it remains a perfect introduction to the shape of every cipher that follows.