Skip to main content
CacheSleuth

Bacon Cipher

Hide letters as five-character A/B or 0/1 groups, with vowel, case, atbash, prime, odd/even, enclosed-shape, and custom-key decoders.

Francis Bacon's cipher hides one message inside another. Originally each letter was carried by switching between two typefaces; today we usually write the carrier as A/B or 0/1. This tool encodes plaintext to Bacon and decodes many disguised forms, case-sensitive, vowels vs. consonants, prime letters, even/odd, enclosed-shape glyphs, the half-alphabet (Atbash) split, or any two characters you choose. If your ciphertext already has only two unique characters, the decoder will pick them up automatically.

Hidden in two typefaces? Extract it from styled text

This is Bacon's original trick: each letter is set in one of two styles. Paste formatted text below (from a web page, a document, an email) and the styling is kept. The tool reads every letter's style, turns the two styles into A/B, and decodes the hidden message. You can also paste raw HTML.

Or paste raw HTML source

Hidden in the characters? Whitespace, invisible, or accents

Some puzzles hide Bacon in the characters themselves: tabs vs spaces, invisible zero-width characters, accented letters (for example à grave vs á acute), homoglyph look-alikes, upside-down or styled letters, markdown emphasis, two emojis or symbols, or single vs double line breaks. Paste the raw text below, exactly as you received it. The inspector lists any hidden characters it finds, and the decoder reads them as Bacon letters or 7-/8-bit ASCII.

Decoders read groups of five carrier symbols. Use the swap buttons if the polarity is reversed.

Decryption modes explained

Auto-detect 2 chars: if the ciphertext has exactly two unique characters (after removing spaces), they are mapped to A and B automatically.

Normal: classic A/B or 0/1 carriers.

Case: uppercase letters are A, lowercase are B (the original Baconian typeface trick).

A–M vs N–Z: the alphabet is split in half, first-half letters/digits are A, second-half are B.

Vowels vs consonants: vowels are A, everything else is B.

Enclosed shapes: letters and digits with closed loops (a b d e g o p q 0 4 6 8 9) are A, the rest B.

Even vs odd: digits and letter positions evaluated for parity, even is A, odd is B.

Prime vs non-prime: prime letters and digits (2 3 5 7 B C E G K M Q S W) are A, the rest B.

Custom characters: pick any two characters from your ciphertext to map to A and B.