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Tap code

Encode or decode messages using tap code, the classic communication method.

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Tap code
Tap code is a simple cipher that prisoners and captives have used for centuries to communicate silently through walls, using a 5×5 grid of 25 letters known as the Polybius square. Each letter corresponds to a position in the grid defined by its row and column, which can be tapped out as a series of taps or communicated as numerical coordinates.
When encoding a message, each letter becomes either a pattern of dots (representing taps, separated by a space) or a pair of numbers showing the row and column. For example, the letter A at position (1,1) becomes ". ." in dot format or "1 1" in number format. Letters are separated by double spaces, and words can be separated by slashes. The letters C and K share the same grid cell, so they encode identically, while I and J are kept separate.
When decoding, you reverse the process: paste the coded message in either dot or number format and the tool converts it back to readable text. Both directions run entirely in your browser, so your messages never leave your device. The live tally counts how many letters were processed, and you can copy the result, download it as a text file, or send it to another tool when done.
FAQ
What is tap code?
Tap code is a communication method that uses a 5×5 grid (Polybius square) to convert letters into patterns of taps, dots, or numbers. Each letter is identified by its row and column position, making it possible to communicate through walls, cell to cell, or using simple taps that do not require elaborate equipment.
What is the Polybius square used in tap code?
The Polybius square is a 5×5 grid containing 25 letters. Letters C and K share one cell. The rows and columns are numbered 1–5, so each letter has a unique coordinate pair (row, column). For example, A is at (1,1), B at (1,2), and Z at (5,5).
What is the difference between dots and numbers formats?
Both formats represent the same information. Dots format uses a period for each tap—one dot for row 1, two for row 2, etc., separated by a space from the column taps. Numbers format directly shows the coordinates as "row col", such as "1 1" for A. Choose dots to simulate traditional tapping; choose numbers for clarity.
Is my text uploaded anywhere?
No. All encoding and decoding happens entirely in your browser. Your messages never leave your device, making tap code a safe method for testing private communication or learning about historical ciphers.