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Send transactions

You can send a transaction in MetaMask using the eth_sendTransaction RPC method.

For example, the following JavaScript gets the user's accounts and sends a transaction when they select each button:

index.js
const ethereumButton = document.querySelector(".enableEthereumButton");
const sendEthButton = document.querySelector(".sendEthButton");

let accounts = [];

sendEthButton.addEventListener("click", () => {
  provider // Or window.ethereum if you don't support EIP-6963.
    .request({
      method: "eth_sendTransaction",
      params: [
        {
          from: accounts[0], // The user's active address.
          to: "0x0000000000000000000000000000000000000000", // Address of the recipient. Not used in contract creation transactions.
          value: "0x0", // Value transferred, in wei. Only required to send ether to the recipient from the initiating external account.
          gasLimit: "0x5028", // Customizable by the user during MetaMask confirmation.
          maxPriorityFeePerGas: "0x3b9aca00", // Customizable by the user during MetaMask confirmation.
          maxFeePerGas: "0x2540be400", // Customizable by the user during MetaMask confirmation.
        },
      ],
    })
    .then((txHash) => console.log(txHash))
    .catch((error) => console.error(error));
});

ethereumButton.addEventListener("click", () => {
  getAccount();
});

async function getAccount() {
  accounts = await provider // Or window.ethereum if you don't support EIP-6963.
    .request({ method: "eth_requestAccounts" });
}

The following HTML displays the buttons:

index.html
<button class="enableEthereumButton btn">Enable Ethereum</button>
<button class="sendEthButton btn">Send ETH</button>

Transaction parameters​

The transaction parameters depend on the transaction type. The following are examples of transaction objects for each type:

{
  nonce: "0x0", // Number of transactions made by the sender before this one.
  gasPrice: "0x09184e72a000", // Gas price, in wei, provided by the sender.
  gasLimit: "0x2710", // Maximum gas provided by the sender.
  to: "0x0000000000000000000000000000000000000000", // Address of the recipient. Not used in contract creation transactions.
  value: "0x0", // Value transferred, in wei.
  data: "0x7f7465737432000000000000000000000000000000000000000000000000000000600057", // Used for defining contract creation and interaction.
  v: "0x1", // ECDSA recovery ID.
  r: "0xa07fd6c16e169f0e54b394235b3a8201101bb9d0eba9c8ae52dbdf556a363388", // ECDSA signature r.
  s: "0x36f5da9310b87fefbe9260c3c05ec6cbefc426f1ff3b3a41ea21b5533a787dfc", // ECDSA signature s.
}

Nonce​

note

MetaMask ignores this field.

In Ethereum, every transaction has a nonce, so each transaction can only be processed by the blockchain once. To be a valid transaction, either:

  • The nonce must be 0.
  • A transaction with a nonce of the previous number, from the same account, must have been processed.

This means that transactions are always processed in order for a given account.

Nonces are easy to mess up, especially when a user is interacting with multiple applications with pending transactions using the same account, potentially across multiple devices. Because of this, MetaMask doesn't allow dapp developers to customize nonces. Instead, MetaMask assists the user in managing their transaction queue themselves.

Gas price​

gasPrice is an optional parameter. It is used in legacy transactions and specifies the gas price the sender is willing to pay for the transaction. MetaMask automatically configures gas settings, but users can also customize these settings.

Gas limit​

gasLimit is an optional parameter. It specifies the maximum amount of gas units the sender is willing to pay for the transaction. MetaMask automatically sets this parameter, but users can also customize their gas settings.

Max priority fee per gas​

maxPriorityFeePerGas is an optional parameter. It is used in EIP-1559 transactions and specifies the maximum fee the sender is willing to pay per gas above the base fee, in order to get their transaction prioritized. MetaMask automatically sets this parameter, but users can also customize their gas settings.

Max fee per gas​

maxFeePerGas is an optional parameter. It is used in EIP-1559 transactions and specifies the maximum total fee (base fee + priority fee) the sender is willing to pay per gas. MetaMask automatically sets this parameter, but users can also customize their gas settings.

To​

The to parameter is a hex-encoded Ethereum address. It's required for transactions with a recipient (all transactions except for contract creation).

Contract creation occurs when there is no to value but there is a data value.

Value​

The value parameter is a hex-encoded value of the network's native currency to send. On Mainnet, this is ether, which is denominated in wei.

These numbers are often far higher precision than native JavaScript numbers, and can cause unpredictable behavior if not anticipated. We recommend using BN.js when manipulating values intended for Ethereum.

Data​

The data parameter is required for smart contract creation.

This field is also used for specifying contract methods and their parameters. See the Solidity ABI spec for more information on how the data is encoded.

Chain ID​

note

MetaMask ignores this field.

The chain ID is derived from the user's current selected network. Use eth_chainId to get the user's chain ID. If you need the network version, use net_version.

In the future, MetaMask might allow connecting to multiple networks at the same time, at which point this parameter will become important, so it might be useful to be in the habit of including it now.

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