UserOperation

The key data structure of account abstraction.

A UserOperation is the key data structure of account abstraction. It represents a new type of transaction that is generated by the user, checked and simulated by the Bundler, and subsequently sent to the EntryPoint contract for validation and execution. The EntryPoint contract verifies the transaction and processes it on-chain through the respective Account contract.

Overview

Similar to a regular transaction UserOperation contains fields such as sender, nonce, callData, and signature. However, a UserOperation is not stored on-chain. Instead, it represents a user's intent to perform a transaction, which is later converted into an actual blockchain transaction. The UserOperation is sent to a Bundler, which listens for these operations, aggregates them (including signature aggregation when possible), and submits them to the EntryPoint contract for execution.

Unlike a traditional blockchain transaction, the signature in a UserOperation can use custom algorithms, unlocking additional functionalities. For instance, the signature can:

• Support threshold signatures for multi-signature wallets.

• Incorporate social recovery mechanisms to restore access in case of lost key pairs.

• Use alternative cryptographic algorithms for specialized security needs.

UserOperation Fields

The fields of a UserOperation are detailed in the table below:

Field	Type	Description
sender	address	The account making the operation
nonce	uint256	Anti-replay parameter; also used as the salt for first-time account creation
initCode	bytes	The initCode of the account (needed if and only if the account is not yet on-chain and needs to be created)
callData	bytes	The data to pass to the sender during the main execution call
callGasLimit	uint256	The amount of gas to allocate the main execution call
verificationGasLimit	uint256	The amount of gas to allocate for the verification step
preVerificationGas	uint256	The amount of gas to pay for to compensate the bundler for pre-verification execution and calldata
maxFeePerGas	uint256	Maximum fee per gas (similar to EIP-1559 max_fee_per_gas)
maxPriorityFeePerGas	uint256	Maximum priority fee per gas (similar to EIP-1559 max_priority_fee_per_gas)
paymasterAndData	bytes	Address of paymaster sponsoring the transaction, followed by extra data to send to the paymaster (empty for self-sponsored transaction)
signature	bytes	Data passed into the account along with the nonce during the verification step

More detailed information about UserOperations and its fields can be found here.