What does an aggregator do in ERC-4337?

An aggregator is an optional helper contract that checks signatures for a group of UserOperations at once, instead of one by one. Some signature types, such as BLS, can be combined into a single signature, so a bundle carries less data and costs less gas to put on-chain. The same mechanism suits proof-based validation, which matters as more apps use zero-knowledge proofs.

What is a paymaster and why is it useful?

A paymaster is a smart contract on EVM chains that pays transaction fees on a user’s behalf when its rules are met, for example only for one app or up to a set budget. It keeps ETH on deposit in advance, and each request it approves is paid from that deposit. Apps use paymasters for gasless onboarding, letting users pay fees in ERC-20 tokens, or sponsoring selected actions.

How does the EntryPoint contract work?

The EntryPoint is the central contract of ERC-4337. Every request from a smart account goes through it. It first checks that the wallet approves the request and that the fee is covered. Then it tells the wallet to do what the user asked, such as sending tokens or making a swap, and pays back the service that delivered the request.

What role do bundlers play in ERC-4337?

Bundlers are the relay layer and the party that actually sends the on-chain transactions of smart accounts. They accept UserOperations, simulate them, group valid ones into one transaction, and submit it to the EntryPoint. Without them, standard RPC cannot accept UserOperations.

Does ERC-4337 require changes to Ethereum's blockchain?

No. ERC-4337 runs on smart contracts and off-chain bundlers, so it needed no hard fork. That is why it reached mainnet years before native account abstraction. Upgrades such as EIP-8141 aim to add native support at the protocol level.