Tap Code Translator
Turn messages into knocks and grid numbers, hear them tapped out, or decode a secret knock. Switch between the prisoners’ tap code and the classic Polybius square.
Some numbers aren’t on the grid, so they show as ?.
Your knocks will appear here.
The tap code grid
Find the row first, then the column. Tap a letter to hear its knocks and add it to your message.
| Row | Column 1 | Column 2 | Column 3 | Column 4 | Column 5 |
|---|---|---|---|---|---|
| Row 1 | |||||
| Row 2 | |||||
| Row 3 | |||||
| Row 4 | |||||
| Row 5 |
| Row | Column 1 | Column 2 | Column 3 | Column 4 | Column 5 |
|---|---|---|---|---|---|
| Row 1 | |||||
| Row 2 | |||||
| Row 3 | |||||
| Row 4 | |||||
| Row 5 |
How to use the tap code
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Find your letter in the 5 by 5 grid. Note its row, then its column.
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Knock the row number, pause, then knock the column number. H is 2 knocks, pause, 3 knocks.
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Leave a longer pause between letters, and a longer one still between words. To decode, count the knocks in pairs.
Use the tap code in your own escape room
Tap code is perfect for spy or prison break themes: knock a code through a wall, hide a number grid on a poster, or play a recording of knocks for players to decode. Our printable escape rooms are full of puzzles like this, ready to print and play tonight.
Tap code questions
What is the tap code?
The tap code is a way to send messages by knocking. Letters sit in a 5 by 5 grid and each one is sent as two groups of knocks: the row, then the column. It became famous when prisoners of war used it to talk through cell walls.
What is the Polybius square?
The Polybius square is the ancient Greek grid the tap code is based on, named after the historian Polybius. It uses the same row and column numbers, but I and J share a square instead of C and K.
Why does the alphabet only have 25 letters?
A 5 by 5 grid has 25 squares, so two letters share one. Tap code drops K and uses C instead, and the Polybius square puts I and J together. Readers can tell which is meant from the word.
Is this tool free?
Yes. It is free to use for puzzles, classrooms, games and secret messages, with no signup.
