Substitution Cipher Solver/Encoder
Encode text with a substitution cipher, or interactively solve one by guessing each letter's mapping.
About this tool
A simple substitution cipher swaps each letter for a fixed different letter throughout. Solving one by hand usually starts from letter frequency (E, T, A are the most common English letters) and common short words — the frequency count under each cipher letter is there to help. Fill in a first guess maps the most common cipher letter to E, the next to T, then A, O, I, N and so on; it's rarely right everywhere, but it usually reveals a few words to build from. Correct any letter by typing over it. Your mapping is kept while you edit the ciphertext, and a letter turns red if you've used the same plain letter twice, which can't happen in a simple substitution.