Last updated October 13, 2026 · Report an error
The Baconian cipher, devised by Francis Bacon in the early 1600s, hides a message by representing each letter as a unique sequence of five "A"s and "B"s.
This tool encodes text into its A/B representation, or decodes an A/B sequence back into text, using the modern 26-letter version where every letter gets its own unique code.
How it works
Each letter's position in the alphabet (A=0 through Z=25) is written as a 5-digit binary number, then every 0 becomes "A" and every 1 becomes "B". To decode, each 5-character group is converted back to binary and then to its matching letter.
- Enter mode.
- Enter text or A/B Code.
- Click Calculate to see your results.
Examples
Encoding "HI"
"HI" becomes "AABBB ABAAA" — each letter always produces exactly 5 characters.
Who should use it
- Puzzle and escape-room style word games.
- Teaching binary number representation through letters.
Industry applications
- Cryptography education
- Games and puzzles
Advantages
- A clear, hands-on introduction to binary encoding of letters.
- Historically notable for hiding messages in plain sight using typeface tricks rather than obvious ciphertext.
Limitations
- No real security once the fixed letter-to-code mapping is known.
Common mistakes to avoid
- Entering a group that isn't exactly 5 characters long, which can't map to a valid letter.
- Mixing up the classical 24-letter historical version (which merges I/J and U/V) with this tool's modern 26-letter version, where every letter is unique.
Best practices
- Use the Baconian cipher for puzzles, teaching binary-to-letter encoding, or as a fun way to introduce how computers represent letters as numbers.
Tips
- If you're decoding a historical Baconian message, check whether it uses the 24-letter I/J and U/V-merged version rather than this tool's 26-letter unique-code version.
Frequently asked questions
Yes, with no signup and no limit on how many conversions you run.
Five binary digits can represent 32 different values, more than enough to give each of the 26 letters a unique A/B code.
No — it's a direct 1-to-1 substitution with no key, so it offers no real security once the pattern is recognized. Historically, its real strength was that the A/B pattern could be hidden inside ordinary-looking text (using two typefaces, for example) rather than the substitution itself being strong.
Space-separated 5-character groups of A and B, like "ABABB ABBAA" — matching what the encode mode produces.