International Code flags are flown to transmit messages between ships. Racing sailboats regularly use them, and some flags have specific uses such as "Q" for requesting permission to use a foreign port.

Full sets of International Code flags are often seen on special occasions like holidays, regattas, or boat parades. Yachts "dress ship" with a colorful display of flags that starts at the forward waterline, up to the mast, then down to the aft waterline.