International Maritime Signal Flags

A standardised set of flags and pennants used to communicate letters, numerals and coded messages visually between vessels or with shore stations.

The International Code of Signals assigns a distinctive design to each letter and numeral, together with substitute pennants and other special flags. A single flag may carry a complete meaning, while groups of flags can form code signals or spell information.

The meaning of a flag used as an International Code signal is not necessarily the same as its spoken phonetic-alphabet word. Visibility, correct hoisting order and an agreed code are essential to interpretation, and modern radio or digital systems often carry information that flags cannot convey efficiently.