How caesar shift detector works
A Caesar cipher has only 25 possible keys, so there is no need to be clever: try every shift and look at what comes out. This tool decrypts the text with each shift from 1 to 25 (shift 0 is the ciphertext itself) and produces 25 candidate plaintexts, ranked so the most English-looking one is first. You do not need to know the key — you just need to recognize your language when you see it.
Ranking is the interesting part. Each candidate gets a chi-squared score comparing its letter frequencies to English: in real English, e appears about 12.7% of the time, t 9.1%, a 8.2%, while z is rare at 0.07%. A candidate whose letters match that diet scores low (good); a scrambled one scores high (bad). On top of that, the scorer looks for actual English words from a built-in common-word list — a candidate containing the, and, or morning is strong evidence, which matters enormously for short messages where letter counts alone are noisy.
The result shows the best candidate's full plaintext plus a ranked table of all 25 shifts with scores and previews, so you can eyeball runner-ups when the top pick is wrong. Decryption is entirely client-side; nothing you paste leaves the browser. The same scoring logic is what cryptanalysis courses teach as frequency analysis — this tool just automates the tedium.