Tools / Bacon Cipher
Bacon Cipher Decoder
Sir Francis Bacon’s cipher encodes each letter as five A/B symbols (5 bits per letter). The fun version in CTF challenges hides those bits inside ordinary text -uppercase vs lowercase, vowels vs consonants, bold vs italic. This tool decodes raw A/B and falls back to case-based and vowel-based plans automatically.
Output
Output appears here.Decrypt accepts A/B and 0/1 input, then falls back to case-based and vowel-based plans for hidden-bit puzzles. The main output uses the modern 26-letter table; when the historical 24-letter table (I=J, U=V) gives a different reading, both are shown.
How it works
Each letter A-Z maps to a 5-bit code. The classic Bacon table (24 letters, treating I/J and U/V as the same) is rare in modern CTF; almost everyone uses the 26-letter variant which this tool implements. Watch for: paragraphs of text where exactly some letters are capitalized, every fifth word italicized, or two distinct-but-similar fonts. Each is carrying one bit.
For pure A/B input where length is not a multiple of 5, double-check that you have not stripped delimiters too aggressively. For unknown ciphers, paste the input into the Cipher Identifier.
Guides that use this tool
Tools that pair with this one
- Morse Code DecoderDecode Morse code to plain text or encode text to Morse code. Supports all letters, digits, and common punctuation.
- Cipher Identifier & Auto-DecoderPaste any ciphertext and the tool auto-runs every common decoder (base64, hex, Morse, ROT, Atbash, Bacon, binary, decimal, URL) and ranks the results by English-likeness.
- Rail Fence CipherEncrypt or decrypt rail fence (zigzag) transposition ciphers. Brute-force across rail counts and offsets to find the right setting fast.
- Frequency AnalysisAnalyze letter frequencies in a substitution cipher and interactively build the decryption mapping with auto-filled guesses.
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