Operations

There are several main components to ERC-4337: UserOperations, Bundler, EntryPoint Contract, Account Contract, Account Factory Contract and Paymaster Contract.

• UserOperation: are pseudo-transaction objects that are used to execute transactions with contract accounts. These are created by the dapp. Wallets should be able to translate regular transactions into UserOperation so dapps' frontends don't need to change anything to support ERC-4337 .

• Bundlers : are actors that package UserOperations from a mempool and send them to the EntryPoint contract on the blockchain.

• EntryPoint: is a smart contract that handles the verification and execution logic for transactions. Account Contracts are smart contract accounts owned by a user.

• Account Contract: is the smart contract wallet of a user.

• Factory Contract: When using a wallet for the first time, the initCode field of the UserOperation is used to specify creation of the smart contract wallet.

• Paymaster Contracts: are optional smart contract accounts that can sponsor gas fees for Account Contracts, or allow their owners to pay for those fees with ERC-20 tokens instead of ETH.

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The lifecycle of transition looks like this:

Source

UserOperation

UserOperation are pseudo-transaction objects that are used to execute transactions with contract accounts. These are created by the dapp. Wallets should be able to translate regular transactions into UserOperation so dapps' frontends don't need to change anything to support ERC-4337.

Field	Type	Description
sender	address	The address of the smart contract account
nonce	uint256	Anti-replay protection; also used as the salt for first-time account creation
initCode	bytes	Code used to deploy the account if not yet on-chain
callData	bytes	Data that's passed to the sender for execution
callGasLimit	uint256	Gas limit for execution phase
verificationGasLimit	uint256	Gas limit for verification phase
preVerificationGas	uint256	Gas to compensate the bundler
maxFeePerGas	uint256	Maximum fee per gas (similar to EIP-1559(opens in a new tab) max_fee_per_gas)
maxPriorityFeePerGas	uint256	Maximum priority fee per gas (similar to EIP-1559 max_priority_fee_per_gas)
paymasterAndData	bytes	Paymaster Contract address and any extra data required for verification and execution (empty for self-sponsored transaction)
signature	bytes	Used to validate a UserOperation along with the nonce during verification