What Is Relayer?
Also known as: Relayer Node, Relay
In short
A relayer is an intermediary software or service that takes transactions, messages, or data from one party and forwards them to a blockchain or another chain. It is widely used in bridges, cross-chain protocols, and transactions where the user does not pay gas.
Relayers do different jobs in different contexts. In cross-chain communication, they watch for proof of an event that took place on one chain and carry it to the destination chain; the IBC protocol in the Cosmos ecosystem relies on relayers that carry packets between chains. The first version of LayerZero also used a design that separates the oracle and relayer roles in message verification.
Another common use is meta-transactions. The user signs the transaction they want to make but does not pay the gas fee; the relayer sends this signed message on-chain from its own account and pays the gas. The fee can be covered by the application, or the relayer can charge the user in tokens. This method makes it easier for new users with no ETH in their wallet to use applications; in account abstraction (ERC-4337), actors called 'bundlers' take on a similar role.
Relayers cannot change the content of transactions, because the user's signature does not allow it; however, they can delay or reorder transactions, or not forward them at all. For this reason, well-designed systems have multiple independent relayers, and anyone can run a relayer. In bridges, whether security rests on the relayer or on on-chain verification is a critical question.
Last updated: · This content is for information purposes only and is not investment advice.