International Code of Signals (ICS) (ICS)

An internationally standardised system of flags, radiotelephony and coded signals for communicating important maritime messages, particularly about safety and navigation.

The code assigns meanings to single-letter flags, multi-flag groups, numeral pennants and selected spoken or Morse forms so vessels and shore stations can exchange concise messages across language barriers. Medical and distress-related sections support specialised communication.

The code does not replace ordinary language, GMDSS procedures or the collision regulations, and a flag’s meaning can depend on whether it is shown alone, in a group or in a racing context. The current official code and correct hoist order must be used.