Type or paste the ciphertext, then press Break code. The ciphertext is decrypted automatically with the best-guessed shift. If the result is incorrect, you can manually try all the different shifts by pressing Up/Down, or by clicking on a table row.
The case is preserved and non-letters are unchanged by encryption or decryption. The automatic decryption is done by trying all 26 possible shift values and calculating the cross-entropy with English letter frequencies (unigram model). The algorithm works best on English text, but in practice it works well on other European languages too.
