HOP¶

Introduction¶

HOP is Polkadot's cross-chain hop protocol — a mechanism for moving assets and messages between chains in the Polkadot ecosystem with more flexibility than a plain XCM transfer. The use case is "hop a transfer through one or more intermediate chains to reach its destination," with HOP handling the per-hop routing, proofs, and cleanup of intermediate state.

For most Product developers, HOP is not something you will reach for in day-one flows. The standard payment patterns — Balances.transfer_keep_alive for merchant flows, Coinage for personhood-aware payments — cover the common cases without needing HOP. HOP becomes relevant when a Product crosses chain boundaries in a way standard XCM does not cleanly handle.

Where HOP Fits¶

Three places HOP shows up in a Product context:

• As a building block under cross-chain payments: Coinage and other payment flows can route through HOP underneath when the sender and recipient are on different chains. The Product surface (Coinage, Balances.transfer_keep_alive) is what a Product calls; HOP is the layer beneath that makes the cross-chain part work.
• As a primitive for cross-chain messaging beyond payments: Moving non-asset payloads (state references, capability handles) across chain boundaries in flows that need more flexibility than plain XCM.
• As a target for node-operator and runtime-developer work: Running a HOP-enabled node, integrating HOP into a new Substrate chain. These node-operator and SDK-integration paths are forthcoming separately.

Where to Go Next¶