> ## Documentation Index
> Fetch the complete documentation index at: https://developers.circle.com/llms.txt
> Use this file to discover all available pages before exploring further.

# 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.

<Note>
  **Gas optimization tip:** If you're writing your own integration, it's more
  gas-efficient to
  [include address conversion logic directly in your contract](https://github.com/circlefin/evm-cctp-contracts/blob/5f1901a9791b18204e8556bb53fb0dfcb05a832a/src/messages/Message.sol#L146)
  rather than calling an external contract.
</Note>

Full contract source code is
[available on GitHub](https://github.com/circlefin/evm-cctp-contracts).

## TokenMessengerV2

### depositForBurn

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

<Note>
  **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](/api-reference/cctp/all/get-fast-burn-usdc-allowance)
  before initiating a transfer to ensure there is enough to complete your
  transfer.
</Note>

**Parameters**

| Field                  | Type      | Description                                                                                                                               |
| ---------------------- | --------- | ----------------------------------------------------------------------------------------------------------------------------------------- |
| `amount`               | `uint256` | Amount of tokens to deposit and burn                                                                                                      |
| `destinationDomain`    | `uint32`  | Destination [domain ID](/cctp/concepts/supported-chains-and-domains#domain-identifiers) 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](/cctp/concepts/fees) paid for transfer, specified in units of `burnToken`                                                   |
| `minFinalityThreshold` | `uint32`  | Minimum [finality threshold](/cctp/concepts/finality-and-block-confirmations) at which burn will be attested                              |

**Example**

```solidity Solidity theme={null}
// 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>
  **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](/api-reference/cctp/all/get-fast-burn-usdc-allowance)
  before initiating a transfer to ensure there is enough to complete your
  transfer.
</Note>

**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](/cctp/references/technical-guide#message-body)) |

## 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](/cctp/references/technical-guide#message-body)) |
| `attestation` | `bytes` | Signed attestation received from Circle's attestation service                         |

**Example**

```solidity Solidity theme={null}
// 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       |