Cipher Lab

Paste ciphertext below and Cipher Lab brute-forces every Caesar shift, Atbash, one-key keyboard shifts, A1Z26 numbers, Morse code, and a frequency-analysis substitution solver, then ranks the candidate decodes by how much of each result matches words in our compiled lexicon.

Try an example:

About this tool & its limits

Every decode is scored against the compiled lexicon of this data release (v1/2026.07-lexical.6), built from the pinned ENABLE, dwyl, CMUdict, Google 10k, and FrequencyWords source artifacts. The score combines how many decoded letters land inside lexicon words (weighted by build-specific commonness bands — ranking bands for this build, not universal usage claims) with a letter-pair plausibility term counted from the same lexicon.

  • Handles monoalphabetic letter ciphers over ASCII a–z only: Caesar/ROT-N (all 25 shifts), Atbash, one-key QWERTY row shifts, A1Z26, Morse, and general substitution. Polyalphabetic ciphers (e.g. Vigenère) and transposition ciphers are out of scope.
  • The substitution solver is a deterministic frequency-analysis hill climb, not an exhaustive search: it needs roughly 40+ letters and can settle on a wrong key for short or unusual texts. Word spacing must be present in the ciphertext for token scoring to help.
  • Results are ranked hypotheses, never guarantees; the top candidate is simply the decode that best matches this build's lexicon.
  • Recognized-word lists are filtered through the engine's offensive-word policy before display.
  • Everything runs on this site's own compiled data; no external services are called.