What is the Baconian cipher?

The Baconian cipher, invented by Francis Bacon, hides each plaintext letter as a group of five symbols, originally As and Bs. By changing fonts or cases, a message can be concealed inside an innocuous text.

What is the difference between the 24-letter and 26-letter variants?

The original cipher used a 24-letter alphabet where I/J and U/V were merged. Later versions expanded it to 26 letters so every letter has its own A/B pattern. This tool lets you pick either one.

Can I decode A/B messages that use 0/1 or X/Y instead?

Yes. Choose your A-like and B-like symbols in the Custom A/B section and the decoder will treat those as the two symbols.

Baconian Cipher Encoder/Decoder (BAC) | A/B, 24-letter, 26-letter, stego

Optional: hide A/B in a cover text

Paste a cover text. We will replace characters with uppercase (=A) and lowercase (=B) according to your encoded sequence. Extra cover characters will stay the same.

Cover text

Stego output (A=UPPER, B=lower)

How the Baconian cipher works

The cipher turns every letter into a block of 5 characters, each either “A” or “B”. For example, in the original 24-letter alphabet:

A = AAAAA

              B = AAAAB

              C = AAABA

              ...

              I/J = ABAAA

              U/V = BAABB

Once you have the A/B sequence, you can hide it in many ways: two fonts, two typefaces, two colors, or simply upper/lowercase. A recipient who knows the scheme can map it back to As and Bs and then to letters.

24 vs 26 letters

24-letter (classic): I=J and U=V are merged to fit 24 patterns.
26-letter (extended): every letter A–Z is unique. Pick this if you don’t want merged letters.

Common decoding problems

Make sure the symbol you use for A and B is the same throughout.
If the encoded message length is not a multiple of 5, the last letter may be incomplete.
If the original text used the 24-letter alphabet, decoding with 26-letter mode will produce odd results.