Flag Semaphore Decoder (Positions to Text)
Decode flag semaphore by clicking the right-arm and left-arm positions to spell out words. Includes a full 26-letter reference chart. Supports letters (A-Z) only.
Flag semaphore alphabet reference chart
| Letter | Right arm | Left arm | Letter | Right arm | Left arm |
|---|---|---|---|---|---|
| A | Lower left (diagonal) | Straight down | B | Left (horizontal) | Straight down |
| C | Upper left (diagonal) | Straight down | D | Straight up | Straight down |
| E | Straight down | Upper right (diagonal) | F | Straight down | Right (horizontal) |
| G | Straight down | Lower right (diagonal) | H | Left (horizontal) | Lower left (diagonal) |
| I | Upper left (diagonal) | Lower left (diagonal) | J | Straight up | Right (horizontal) |
| K | Lower left (diagonal) | Straight up | L | Lower left (diagonal) | Upper right (diagonal) |
| M | Lower left (diagonal) | Right (horizontal) | N | Lower left (diagonal) | Lower right (diagonal) |
| O | Left (horizontal) | Upper left (diagonal) | P | Left (horizontal) | Straight up |
| Q | Left (horizontal) | Upper right (diagonal) | R | Left (horizontal) | Right (horizontal) |
| S | Left (horizontal) | Lower right (diagonal) | T | Upper left (diagonal) | Straight up |
| U | Upper left (diagonal) | Upper right (diagonal) | V | Straight up | Lower right (diagonal) |
| W | Upper right (diagonal) | Right (horizontal) | X | Lower right (diagonal) | Upper right (diagonal) |
| Y | Upper left (diagonal) | Right (horizontal) | Z | Lower right (diagonal) | Right (horizontal) |
Tips
- The reference tiles are drawn from the signaller's own point of view. Since the signaller faces the viewer, the right arm appears on the left side of the screen and the left arm on the right side.
- Keep clicking letters to build up a word. If you make a mistake, use "Delete last letter" to remove only the most recent letter.
- Use "Add space" between words to keep your spelled-out message readable, similar to how a real signaller pauses between words.
- Only letters (A-Z) are supported. Semaphore numerals use a separate system that requires a dedicated switch-over signal, so they're intentionally out of scope here.
Frequently asked questions
Side Note — The 'reading' skill flag semaphore trained
Flag semaphore was standardized by 19th-century navies as a visual communication method, and before radio became practical it played a critical role in ship-to-ship and ship-to-shore signalling. Despite its simple mechanism — just moving a flag-holding arm through eight 45-degree positions — well-trained signallers could reportedly exchange more than a dozen words per minute.
Experienced signallers trained themselves to instantly read a flag's position swaying far away on a distant ship's deck, drilling the "position patterns" into muscle memory through repetition. It's not unlike how a modern typist can type without consciously thinking about the keyboard layout — a form of training that converts visual information into language almost instantly.
As radio communication matured, flag semaphore's practical importance declined, but it's still taught today as a backup communication method for when radios fail or radio silence is required — a basic skill kept alive by navies around the world and by outdoor programs in the Scouting movement.