What is flag semaphore?

Flag semaphore is a visual signalling system where a person holds a flag in each hand and sets the arms to fixed angles to represent letters and numbers. It was widely used at sea before radio.

How are the arm angles described?

Each arm points to one of eight clock-like directions: down, low, out (horizontal), high, or up, on the left or right side. The two angles together uniquely identify a letter.

Are numbers supported?

Semaphore signals letters only; numbers are sent by first showing the special Numerals sign, after which A–K stand for 1–0. This encoder spells letters and leaves digits unchanged with a note.

Is it case sensitive?

No. Semaphore has no case, so uppercase and lowercase letters produce the same arm positions. Spaces between words are preserved as a separator.

Is my text uploaded anywhere?

No. The conversion uses a built-in position table and runs entirely in your browser; nothing is sent to a server.

Semaphore Flag Encoder

Flag semaphore is a visual telegraphy system in which a signaller holds a coloured flag in each hand and places the two arms at fixed angles to spell out a message. It was the standard ship-to-ship method before radio and is still part of maritime and scouting training. This encoder converts text into the standard semaphore alphabet, describing the angle of each arm for every letter.

How it works

Imagine the signaller’s body as a clock centre. Each arm can point in one of eight directions: straight down, low (down-diagonal), out (horizontal), high (up-diagonal), and up. The semaphore alphabet is built systematically: A is left-arm low-left / right-arm down, and the pattern rotates one arm at a time through the circle.

This tool stores the canonical left/right angle pair for each of the 26 letters and prints them as readable descriptions such as Left: out-left, Right: down. Words are separated by a blank line so message structure is clear.

Example

The letter A is Left: low-left, Right: down, and R is Left: out-left, Right: high-right. Spelling a short word shows one labelled line per letter, which a learner can use to practise the arm movements in front of a mirror.