Backend Relayer

What is Backend Relayer?

A backend relayer is a server that submits blockchain transactions on behalf of users. It acts as an intermediary that handles the technical process of broadcasting a transaction to the network.

How does Backend Relayer work?

1. A user signs a transaction or a message off-chain using their private key.
2. The signed data is sent to the backend relayer via an API.
3. The relayer wraps the user's data into a new transaction and signs it.
4. The relayer pays the gas fee and broadcasts the transaction to the blockchain.
5. The smart contract on-chain verifies the user's original signature before executing.

Why does Backend Relayer matter?

Relayers enable "gasless" transactions where users don't need to hold the native network token (like ETH) to interact with a dApp. This significantly lowers the barrier to entry for new Web3 users.

Key features of Backend Relayer

• Enables gasless user experiences
• Abstracted transaction submission
• Centralized but non-custodial (cannot change user intent)
• Handles gas price management and retries
• Essential for many Account Abstraction (ERC-4337) flows

Examples of Backend Relayer

• A game paying the gas fees for its players to mint in-game items.
• A DEX allowing users to pay for gas using stablecoins instead of ETH.
• Biconomy and OpenGSN, which provide infrastructure for relaying transactions.