You can connect to Blast by instantiating a new web3.js Web3 object with a RPC URL of the Blast network.

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Mainnet

const { Web3 } = require('web3');

const web3 = new Web3('https://rpc.blast.io');

See Network Information for additional mainnet RPC endpoints.

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Testnet

const { Web3 } = require('web3');

const web3 = new Web3('https://sepolia.blast.io');