web/apps/base-docs/docs/tools/web3.md

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title	slug	description	keywords	hide_table_of_contents
web3.js	/tools/web3	Documentation for using web3.js, a JavaScript library for interacting with EVM-compatible blockchains. This page covers installation, setup, connecting to the Base network and interacting with smart contracts.	web3.js Base Base mainnet Base testnet Base network JavaScript EVM client library blockchain smart contracts Ethereum RPC URL	true

web3.js

web3.js is a JavaScript library that allows developers to interact with EVM-compatible blockchain networks.

You can use web3.js to interact with smart contracts deployed on the Base network.

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Install

To install web3.js run the following command:

npm install web3

Setup

Before you can start using web3.js, you need to import it into your project.

Add the following line of code to the top of your file to import web3.js:

//web3.js v1
const Web3 = require('web3');

//web3.js v4
const { Web3 } = require('web3');

Connecting to Base

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

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

const web3 = new Web3('https://mainnet.base.org');

:::info

To alternatively connect to Base Sepolia (testnet), change the above URL from https://mainnet.base.org to https://sepolia.base.org.

:::

Accessing data

Once you have created a provider, you can use it to read data from the Base network.

For example, you can use the getBlockNumber method to get the latest block:

async function getLatestBlock(address) {
  const latestBlock = await web3.eth.getBlockNumber();
  console.log(latestBlock.toString());
}

Deploying contracts

Before you can deploy a contract to the Base network using web3.js, you must first create an account.

You can create an account by using web3.eth.accounts:

const privateKey = “PRIVATE_KEY”;
const account = web3.eth.accounts.privateKeyToAccount(privateKey);

:::info

PRIVATE_KEY is the private key of the wallet to use when creating the account.

:::

Interacting with smart contracts

You can use web3.js to interact with a smart contract on Base by instantiating a Contract object using the ABI and address of a deployed contract:

const abi = [
… // ABI of deployed contract
];

const contractAddress = "CONTRACT_ADDRESS"

const contract = new web3.eth.Contract(abi, contractAddress);

Once you have created a Contract object, you can use it to call desired methods on the smart contract:

async function setValue(value) {
  // write query
  const tx = await contract.methods.set(value).send();
  console.log(tx.transactionHash);
}

async function getValue() {
  // read query
  const value = await contract.methods.get().call();
  console.log(value.toString());
}

:::info

For more information on deploying contracts on Base, see Deploying a Smart Contract.

:::