Retrieve finalized L2 blocks

A finalized L2 block is a block on an L2 blockchain (Linea) that has been confirmed and validated by the L1 blockchain (Ethereum), ensuring its immutability and security.

Linea doesn't currently support the Ethereum-standard finalized block parameter tag, meaning you cannot use the tag in JSON-RPC API calls to retrieve blocks that have been confirmed by the L1 network. This includes, for example, methods where you can specify a block parameter, such as linea_estimateGas.

note

Support for the finalized block parameter is planned in a future Linea release.

This limitation requires you to query the Linea L1 rollup contract to retrieve the value of the current finalized L2 block number stored in the currentL2BlockNumber variable.

Prerequisites

Download and install Node.js

Create the script

In your project folder, initialize the project and install the web3 package:
```
npm init -y
```
```
npm install web3
```

Create a JavaScript file (for example index.js) and copy the following code:

info

Update the Infura endpoint with your API key, or add a different RPC provider.

index.js
const { Web3 } = require("web3")

// Connect to an Ethereum node (e.g., Infura)
const web3 = new Web3(
  new Web3.providers.HttpProvider(
    `https://mainnet.infura.io/v3/<YOUR-API-KEY>`
  )
)
// Define the minimal ABI to obtain the current finalized block number
const lineaRollupAbi = [
  {
    "constant": true,
    "inputs": [],
    "name": "currentL2BlockNumber",
    "outputs": [
      {
        "name": "",
        "type": "uint256"
      }
    ],
    "payable": false,
    "stateMutability": "view",
    "type": "function"
  }
];

// Define the contract address
const lineaRollupAddress = '0xd19d4b5d358258f05d7b411e21a1460d11b0876f';

// Create a contract instance
const lineaRollupContract = new web3.eth.Contract(lineaRollupAbi, lineaRollupAddress);

// Function to get the finalized L2 block number
async function getFinalizedL2BlockNumber() {
  try {
    const currentL2BlockNumber = await lineaRollupContract.methods.currentL2BlockNumber().call();
    const blockNumberHex = '0x' + BigInt(currentL2BlockNumber).toString(16); // Convert BigInt to hex string

    console.log('Finalized L2 Block Number:', currentL2BlockNumber.toString()); // Print BigInt as string
    console.log('Finalized L2 Block Number (Hex):', blockNumberHex);

    return { blockNumber: currentL2BlockNumber, blockNumberHex };
  } catch (error) {
    console.error('Error fetching L2 block number:', error);
  }
}

// Call the function
getFinalizedL2BlockNumber();

In the project directory, run the script:
```
node index.js
```

Prerequisites​

Create the script​

Prerequisites

Create the script