🥓 Bacon's Cipher (Baconian)
Every letter as five A's and B's — Bacon's cipher, designed to be hidden inside ordinary-looking text. Encode and decode locally.
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How the bacon's cipher (baconian) works
Devised by Francis Bacon around 1605, this cipher represents each letter as a group of five symbols drawn from just two options — here written as A and B (the five-bit binary code of the letter's position). The clever part historically was steganography: the two symbols could be hidden as two typefaces, two handwriting styles, or any binary distinction in a normal-looking message, so the very existence of the secret was concealed. This tool uses the unique 26-letter variant so every letter round-trips exactly.
Bacon's original 24-letter version merged I/J and U/V into single codes (there was no distinct J or U in his alphabet), which makes decoding ambiguous; this tool uses the modern 26-letter variant where each letter has its own code, so text encodes and decodes cleanly. The real historical trick wasn't the A/B code itself but hiding it in plain sight — two fonts carrying a message no one knew was there.
Frequently asked questions
What is Bacon's cipher?
A cipher from Francis Bacon (c. 1605) that encodes each letter as five symbols of two kinds — commonly written AAAAA, AAAAB, and so on. It's really a way to hide a message: the two symbols can be disguised as two fonts or styles in ordinary text.
Why five letters per character?
Five binary symbols give 2⁵ = 32 combinations, enough to cover all 26 letters with room to spare. It is effectively a 5-bit binary encoding written with A and B instead of 0 and 1.
What's the difference between the 24- and 26-letter versions?
Bacon's original alphabet had no separate J or U, so I/J and U/V shared codes — which makes decoding ambiguous. This tool uses the 26-letter variant where every letter is distinct, so it round-trips perfectly.
Was Bacon's cipher actually used to hide messages?
That was its whole point — steganography. By setting the two symbols as two typefaces or handwriting styles, a message could be concealed inside an innocent-looking text so that no one suspected a cipher was present at all.
Is it computed locally?
Yes — encoding and decoding happen in your browser.