Definition
A cross-chain messaging protocol is a specification and set of rules that governs how structured messages are formatted, validated, and relayed between distinct blockchain networks. It defines the semantics for encoding state or intent, the verification assumptions for accepting messages originating on foreign chains, and the canonical interfaces that applications use to reference and interpret cross-chain data without prescribing a particular bridging or transport implementation.
In Simple Terms
A cross-chain messaging protocol is a formal rulebook for how blockchains talk to each other using messages. It sets the structure and meaning of those messages and the conditions under which they are accepted on another chain, without being tied to one specific bridge design or transport method.
Context and Usage
The term is commonly used in discussions about blockchain interoperability, where applications require consistent semantics for sending and receiving information across heterogeneous chains. It appears in protocol design documents, security analyses of cross-chain systems, and specifications that separate message semantics from underlying transport layers such as bridges, oracles, or data availability systems. It also frames how developers reason about cross-domain state references and intent propagation.