EVM contract interfaces

Public methods and events for CCTP smart contracts on EVM-compatible blockchains

This page documents the public methods and events exposed by CCTP smart contracts on EVM-compatible blockchains.

Contract responsibilities

• TokenMessengerV2: Entrypoint for crosschain USDC transfer. Routes messages to burn USDC on a source blockchain and mint USDC on a destination blockchain.
• MessageTransmitterV2: Generic message passing. Sends all messages on the source blockchain and receives all messages on the destination blockchain.
• TokenMinterV2: Responsible for minting and burning USDC. Contains blockchain-specific settings used by burners and minters.
• MessageV2: Provides helper functions for crosschain transfers, such as bytes32ToAddress and addressToBytes32, which are commonly used when bridging between EVM and non-EVM blockchains.

Gas optimization tip: If you’re writing your own integration, it’s more gas-efficient to include address conversion logic directly in your contract rather than calling an external contract.

Full contract source code is available on GitHub.

TokenMessengerV2

depositForBurn

Deposits and burns tokens from sender to be minted on destination domain. Minted tokens will be transferred to mintRecipient.

Note: There is a $10 million limit on the amount of USDC that can be burned in a single CCTP transaction. If the amount exceeds this limit, the transaction will revert. If you need to transfer more than this limit, break up your transfers into multiple transactions.

For Fast Transfers, you should always check the remaining allowance before initiating a transfer to ensure there is enough to complete your transfer.

Parameters

Field	Type	Description
amount	uint256	Amount of tokens to deposit and burn
destinationDomain	uint32	Destination domain ID to send the message to
mintRecipient	bytes32	Address of mint recipient on destination domain (must be converted to 32 byte array, that is, prefix with zeros if needed)
burnToken	address	Address of contract to burn deposited tokens on local domain
destinationCaller	bytes32	Address as bytes32 which can call receiveMessage on destination domain. If set to bytes32(0), any address can call receiveMessage
maxFee	uint256	Maximum fee paid for transfer, specified in units of burnToken
minFinalityThreshold	uint32	Minimum finality threshold at which burn will be attested

Example

Solidity

// Burn 100 USDC on Ethereum for minting on Avalanche
uint256 amount = 100 * 10**6; // 100 USDC
uint32 destinationDomain = 1; // Avalanche
bytes32 mintRecipient = bytes32(uint256(uint160(recipientAddress)));
address burnToken = 0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48; // USDC on Ethereum
bytes32 destinationCaller = bytes32(0); // Anyone can call receiveMessage
uint256 maxFee = 1000; // 0.001 USDC max fee
uint32 minFinalityThreshold = 1000; // Fast Transfer

tokenMessenger.depositForBurn(
  amount,
  destinationDomain,
  mintRecipient,
  burnToken,
  destinationCaller,
  maxFee,
  minFinalityThreshold
);

depositForBurnWithHook

Deposits and burns tokens from sender to be minted on destination domain, and emits a crosschain message with additional hook data appended. In addition to the standard depositForBurn parameters, depositForBurnWithHook accepts a dynamic-length hookData parameter, allowing you to include additional metadata that can trigger custom logic on the destination blockchain.

Note: There is a $10 million limit on the amount of USDC that can be burned in a single CCTP transaction. If the amount exceeds this limit, the transaction will revert. If you need to transfer more than this limit, break up your transfers into multiple transactions.

For Fast Transfers, you should always check the remaining allowance before initiating a transfer to ensure there is enough to complete your transfer.

Parameters

Field	Type	Description
amount	uint256	Amount of tokens to burn
destinationDomain	uint32	Destination domain to send the message to
mintRecipient	bytes32	Address of mint recipient on destination domain (must be converted to 32 byte array, that is, prefix with zeros if needed)
burnToken	address	Address of contract to burn deposited tokens on local domain
destinationCaller	bytes32	Address as bytes32 which can call receiveMessage on destination domain. If set to bytes32(0), any address can call receiveMessage
maxFee	uint256	Maximum fee paid for transfer, specified in units of burnToken
minFinalityThreshold	uint32	Minimum finality threshold at which burn will be attested
hookData	bytes	Additional metadata attached to the attested message, used to trigger custom logic on the destination blockchain

getMinFeeAmount

Calculates and returns the minimum fee required for a given amount in a Standard Transfer. If the minimum fee (per unit of burnToken) is non-zero, the specified maxFee must be at least the returned minimum fee. Otherwise, the burn will revert onchain.

Parameters

Field	Type	Description
amount	uint256	The amount used to compute the minimum fee. Must be greater than 1 if standard fee is applied

handleReceiveFinalizedMessage

Handles incoming message received by the local MessageTransmitter. For a burn message, mints the associated token to the requested recipient on the local domain. Validates the function sender is the local MessageTransmitter, and the remote sender is a registered remote TokenMessenger for remoteDomain.

This method is called for messages where finalityThresholdExecuted ≥ 2000 (Standard Transfer).

Parameters

Field	Type	Description
remoteDomain	uint32	The domain where the message originated from
sender	bytes32	The sender of the message (remote TokenMessenger)
finalityThresholdExecuted	uint32	Specifies the level of finality Circle signed the message with
messageBody	bytes (dynamic length)	The message body bytes

handleReceiveUnfinalizedMessage

Handles incoming message received by the local MessageTransmitter. For a burn message, mints the associated token to the requested recipient on the local domain. Similar to handleReceiveFinalizedMessage, but is called for messages which are not finalized (finalityThresholdExecuted < 2000) such as Fast Transfers.

Unlike handleReceiveFinalizedMessage, handleReceiveUnfinalizedMessage processes messages with:

• expirationBlock: If expirationBlock ≤ blockNumber on the destination domain, the message will revert and must be re-signed without the expiration block.
• feeExecuted: If nonzero, the feeExecuted amount is minted to the feeRecipient.

Parameters

Field	Type	Description
remoteDomain	uint32	The domain where the message originated from
sender	bytes32	The sender of the message (remote TokenMessenger)
finalityThresholdExecuted	uint32	Specifies the level of finality Circle signed the message with
messageBody	bytes (dynamic length)	The message body bytes (see Message format)

MessageTransmitterV2

receiveMessage

Receives message on destination blockchain by passing message and attestation. Emits MessageReceived event. Messages with a given nonce can only be broadcast successfully once for a pair of domains. The message body of a valid message is passed to the specified recipient for further processing.

Parameters

Field	Type	Description
message	bytes	Encoded message (see Message format)
attestation	bytes	Signed attestation received from Circle’s attestation service

Example

Solidity

// Mint USDC on destination chain
bytes memory message = attestationData.message;
bytes memory attestation = attestationData.attestation;

messageTransmitter.receiveMessage(message, attestation);

sendMessage

Sends a message to the recipient on the destination domain. Emits a MessageSent event which will be attested by Circle’s attestation service.

Parameters

Field	Type	Description
destinationDomain	uint32	Destination domain ID to send the message to
recipient	bytes32	Address of recipient on destination domain
destinationCaller	bytes32	Address as bytes32 which can call receiveMessage on destination domain. If set to bytes32(0), any address can call receiveMessage
minFinalityThreshold	uint32	Minimum finality threshold requested. A value greater than 2000 is interpreted as 2000 (finalized). Thresholds: 1000 for Fast Transfer (confirmed), 2000 for Standard Transfer (finalized)
messageBody	bytes	application-specific message to be handled by recipient

Events

DepositForBurn

Emitted when USDC is burned on the source blockchain.

Parameters

Field	Type	Indexed	Description
nonce	uint64	Yes	Unique message identifier
burnToken	address	Yes	Address of token burned
amount	uint256	No	Burn amount
depositor	address	Yes	Address of depositor
mintRecipient	bytes32	No	Mint recipient address on destination domain
destinationDomain	uint32	No	Destination domain identifier
destinationTokenMessenger	bytes32	No	Address of TokenMessenger contract on destination domain
destinationCaller	bytes32	No	Authorized caller of receiveMessage on destination domain
maxFee	uint256	No	Maximum fee for the transfer
minFinalityThreshold	uint32	No	Minimum finality threshold at which burn will be attested

MessageSent

Emitted when a message is sent from the source blockchain.

Parameters

Field	Type	Indexed	Description
message	bytes	No	Raw bytes of message

MessageReceived

Emitted when a message is received on the destination blockchain.

Parameters

Field	Type	Indexed	Description
caller	address	Yes	Address that called receiveMessage
sourceDomain	uint32	Yes	Source domain identifier
nonce	uint64	Yes	Unique message identifier
sender	bytes32	No	Address of message sender on source domain
messageBody	bytes	No	Message body

MintAndWithdraw

Emitted when USDC is minted on the destination blockchain.

Parameters

Field	Type	Indexed	Description
mintRecipient	address	Yes	Address receiving minted USDC
amount	uint256	No	Amount minted
mintToken	address	Yes	Address of token minted