This FAO publication provides a comprehensive introduction to blockchain, covers smart contracts, and explores how they relate to blockchain with an example of their use in seafood value chains. It examines major development and operational considerations for blockchain applications. It also analyses the seafood supply chain with considerations on flag, coastal, port, processing and market countries. The study identifies general control elements (critical tracking events and corresponding key data elements) that form the basis for traceability monitoring and acquisition, and summarises th suitability of blockchain application. It also investigates considerations for legality, transparency, species fraud and food safety.