Code of signals have been published since the beginning of the 19th Century to provide mariners with an internationally accepted, common system for communication at sea. Each signal within the International Code of Signals has a complete meaning, which ensures that specific situations related to safety can be clearly communicated through various means, even when language difficulties arise.

Since its first edition, published in 1965, amendments to the Code have been adopted by the Maritime Safety Committee of the International Maritime Organization (IMO) resulting in four subsequent editions. The fourth edition of the Code (2005 edition) incorporated all amendments up to MSC 73 in December 2000. The International Code of Signals has not been amended since its fourth edition and this current edition comprises only minor editorial improvements and a new cover. Therefore, both the 2005 edition and this edition of the Code are considered equally valid.

Edition: 2021