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Bacon Cipher Decoder / Encoder

A Bacon cipher decoder recovers a message hidden five symbols per letter in two kinds of character — originally two typefaces, in puzzles usually capitals and lowercase, bold and plain letters, or any two symbols. This one finds the hiding place itself, tries both ways round under all three Baconian alphabets, and ranks the readings, entirely in your browser.

Paste the a/b text, any two symbols, or a cover text whose capitals or styled letters hide the message. Every hiding place, both ways round, under all three alphabets.

  • letter case · lowercase is a · 26 letters
    Best match
    BACONAA
  • letter case · lowercase is a · Bacon's 24 letters
    BACPOAA
  • letter case · lowercase is a · 26 letters from aaaab
    3 unused codes
    A�BNM��
  • letter case · capitals are a · Bacon's 24 letters
    5 unused codes
    ���ST��
  • letter case · capitals are a · 26 letters
    5 unused codes
    ���RS��
  • letter case · capitals are a · 26 letters from aaaab
    5 unused codes
    ���QR��

Cover texts usually run on past the message, so letters after it decode to filler — typically a run of A's. Spaces aren't part of the cipher, so words come back run together.

About Bacon Cipher Decoder / Encoder

Francis Bacon devised the cipher in 1605 and published it in De Augmentis Scientiarum in 1623. Each letter becomes five symbols, each one of two kinds, a or b: A is aaaaa, B is aaaab, and so on. The point is that a and b don't have to look like letters at all. Bacon wrote an innocent cover text in two slightly different typefaces, so the message sat in which typeface each letter used, invisible to anyone who didn't know to look — steganography as much as cryptography. Three alphabets are in use and nothing in the ciphertext says which. Bacon's original has 24 letters, with I and J sharing a code and so do U and V. The common modern version gives all 26 letters their own code, A = aaaaa to Z = bbaab, and a third counts from A = aaaab. Nor is it written which typeface means a. So this decoder tries every combination and ranks the readings by how English their letter pairs look. It also finds the hiding place for you. Paste a/b text or any two distinct symbols — 0 and 1, two emoji — and they're read directly. Paste a cover text and it looks at letter case, the usual trick in puzzles, and at styled Unicode letters such as 𝐛𝐨𝐥𝐝 or 𝘪𝘵𝘢𝘭𝘪𝘤 mixed in with plain ones, the closest plain text gets to Bacon's two typefaces. Cover texts usually run on past the message, so the end of a reading is often filler. Encoding gives you the a/b groups and can hide them in a cover text of your own, one letter per symbol. The cipher has a curious footnote. In the early 1900s Elizabeth Wells Gallup claimed to find Bacon's cipher in the typefaces of Shakespeare's First Folio, proof, she said, that Bacon wrote the plays. William and Elizebeth Friedman, who began their codebreaking careers working alongside her, later showed that the method didn't hold up.

What Bacon Cipher Decoder / Encoder does

  • Finds the hiding place: two symbols, letter case, or plain and styled Unicode letters
  • Tries both polarities under all three Baconian alphabets, best match first
  • Bacon's 24-letter alphabet, the 26-letter version, and the one counting from aaaab
  • Encodes to a/b or 0/1 groups
  • Hides a message in your own cover text through letter case

When to reach for Bacon Cipher Decoder / Encoder

  • Solving a CTF or puzzle-hunt clue where some letters are capitalised for no reason
  • Decoding a run of two symbols, emoji or 0s and 1s in groups of five
  • Hiding a short message in an innocent-looking sentence

How to use Bacon Cipher Decoder / Encoder

  1. 01

    Paste the text

    a/b text, any two symbols, or a cover text where some letters look different — capitals, bold or italic.

  2. 02

    Read the best match

    Every hiding place the text uses is tried both ways round under all three alphabets, most English-looking first.

  3. 03

    Ignore the filler

    A cover text longer than the message decodes to junk after it, usually a run of A's.

  4. 04

    Encode your own

    Switch to Encode for the a/b groups, and paste a cover text to hide them in its letter case.

When to use Bacon Cipher Decoder / Encoder vs alternatives

AlternativeUse Bacon Cipher Decoder / Encoder when…Use the alternative when…
A Bacon cipher decoder that only reads a/b textthe message is hidden in a cover text's capitals or styled letters, or you don't know which alphabet or polarity was used.you already have clean a/b text and know the alphabet.
CyberChef's Bacon Cipher Decodeyou want the hiding place found and every alphabet and polarity ranked in one go.you're building a longer CyberChef recipe around it.

Frequently asked questions

How does Bacon's cipher work?
Each letter becomes five symbols, each either a or b: A is aaaaa, B is aaaab, C is aaaba, and so on. The a's and b's are then hidden in a cover text written in two typefaces, one for a and one for b, so the secret is in how the letters look rather than what they say. To decode, write down a or b for each letter's typeface, split into groups of five and look the groups up.
How do I decode a Bacon cipher hidden in capital letters?
Paste the whole text. Each letter counts as one symbol — lowercase as one kind, capitals as the other — and every five letters make one letter of the message. The tool tries both ways round and all three alphabets and puts the reading that looks most like English first. Spaces and punctuation are ignored, and letters after the end of the message decode to filler.
What is the difference between the 24 and 26-letter Bacon alphabets?
Bacon's original alphabet has 24 letters because I and J, and U and V, were treated as the same letters in his day, so each pair shares a code. The modern 26-letter version gives every letter its own code, which shifts everything from J onwards: K is ababa in the 26-letter alphabet but abaab in Bacon's. A third version counts from A = aaaab. Messages decode as near-nonsense under the wrong alphabet, so this tool tries all three.
Can the a and b be things other than letters?
Yes — anything with two distinct forms works, which is why puzzles use it so much: two typefaces, bold and plain, capitals and lowercase, two emoji, 0 and 1, even two kinds of flower in a picture. Paste any text made of exactly two symbols and the tool reads them in groups of five, trying each symbol as a.
Did Bacon hide messages in Shakespeare's plays?
That was the claim of Elizabeth Wells Gallup, who in the early 1900s said she had found Bacon's cipher in the typefaces of Shakespeare's First Folio. William and Elizebeth Friedman, who began their codebreaking careers working with her, later examined the method and showed it didn't hold up — the typeface variations weren't consistent enough to carry a message.

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