Tap code chart
Every letter, A to Z.
- A
- B
- C
- D
- E
- F
- G
- H
- I
- J
- K
- L
- M
- N
- O
- P
- Q
- R
- S
- T
- U
- V
- W
- X
- Y
- Z
Where it comes from
American prisoners of war in Hanoi's Hỏa Lò prison taught each other this code from 1965, tapping through cell walls they could not see past. Letters sit in a five-by-five square, and K is tapped as C. Knock the row, pause, knock the column.
A message worth knowing: GBU. God bless you. Prisoners in Hỏa Lò tapped it to the next cell at night before they slept.
Learn it by heart
This is the cipher desk from Covert Mail, our free app for learning codes. The app teaches Tap code a few characters at a time, plans practice around the ones you miss, and keeps an archive of famous real messages to unlock. It is coming soon to the App Store and Google Play.
Coming soon to the App Store and Google Play
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