The Bacon cipher writes each letter as five signs of two kinds, A and B, like a binary code: HELLO is AABBB AABAA ABABA ABABA ABBAB. The signs can be swapped for 0 and 1 or dots and dashes, or the message can be hidden in ordinary text: a lowercase letter means A, a capital means B.
Everything runs in your browser — the text goes nowhere
The letter's number is written as five binary signs: A for zero, B for one. 32 combinations, enough for 32 letters.
24 Latin letters
I = J · U = V
Bacon made the cipher for the 17th-century Latin alphabet, where these pairs were one letter.
Hide it in text
thE QUiCk brown fox
Sign A is a lowercase cover letter, B a capital. The text looks ordinary, and the message is read from the case.
04
Frequently asked questions
Each letter has a number, written as five binary signs: A for zero and B for one. The classic Latin version has 24 letters, with I and J, U and V the same; the Russian version has 32 letters without Ё. Five signs give exactly 32 combinations, so the ciphertext always comes in groups of five, and the table on this page shows each code.
Turn on Hide in text and write a cover, any harmless text. Each letter of the cover becomes one sign: lowercase for A, capital for B. Every letter of the message needs five cover letters, and if there are not enough we say how many to add. Anyone who knows the trick reads the message on the Decode tab in the same mode.
Francis Bacon made the cipher for the Latin alphabet of his time, where I and J, U and V were forms of one letter. That gives 24 letters: J is encoded as I and V as U, so decoding shows i and u in their place. This is how the cipher works, not a mistake. The Russian version uses 32 letters, with ё written as е.
Paste the groups of five into the Decode tab and choose the same signs that were used to encode: A and B, 0 and 1, Russian а and б, or dot and dash. Spaces between groups are optional, but each word must have a multiple of five signs. If the count is off or a stray character appears, we say so instead of guessing.
Francis Bacon, the English philosopher and statesman, published the biliteral cipher in 1623 in his treatise De Augmentis Scientiarum. His main idea was not the code itself but hiding a message inside any text by changing the shape of letters. It is one of the first known schemes of steganography, secret writing that hides the very fact of a message.
Not our site: encoding and finding the hidden message happen in your browser, and neither the text nor the cover is sent to a server or written into the address. Only the Share button creates a link with the text. An attentive reader, however, may notice odd capitals in the cover: the cipher hides a message from a casual glance, not from someone who knows the trick.