What is Web3.js: Basic to Advanced Guide for Developers

It’s necessary to understand the significance of Web3js in blockchain technology. Web3js serves as a crucial tool in the development of decentralized applications (dApps) on the Ethereum blockchain. This JavaScript library facilitates seamless interaction between your application and the blockchain, allowing for the integration of smart contracts, transactions, and data retrieval.

In this comprehensive guide, we will research into the intricacies of Web3js, exploring its functionality, features, and practical applications.

Whether you are a developer looking to enhance your dApp capabilities or simply curious about the next generation of the internet, this article will provide you with everything you need to know about Web3js.

What is Web3.js?

Web3.js is a JavaScript library that allows developers to interact with the Ethereum blockchain and build decentralized applications (dApps). It provides a simple and user-friendly interface for accessing blockchain data and executing smart contracts.

With Web3.js, developers can seamlessly integrate blockchain functionality into their web applications and leverage the benefits of decentralized technology.

Web3.js plays a crucial role in the adoption and advancement of blockchain technology in the field of web development.

Key Components and Functions of Web3.js

Web3.js is an integral part of Ethereum development, providing a collection of libraries that enable developers to interact with local or remote Ethereum nodes conveniently.

It plays a crucial role in facilitating communication between clients and the Ethereum blockchain.

Here are some key components and functions of Web3.js:

  • Utils: The web3-utils package is an essential part of Web3.js. It allows developers to perform a range of tasks critical to Ethereum development, including converting data formats and checking addresses.
  • Providers: Web3.js providers are objects that enable connectivity with the Ethereum network in various ways. These providers facilitate your web application’s connection to an Ethereum node using HTTP, IPC, or WebSocket.
  • Smart Contract Interaction: Web3.js provides functions that allow developers to deploy and interact with smart contracts on the Ethereum blockchain. These smart contracts are vital components of Decentralized Applications (DApps).
  • Transactions: Using Web3.js, developers can create, sign, and track transactions on the Ethereum blockchain. This feature is highly beneficial for building applications that involve cryptocurrency transactions.
  • Events and Filters: Web3.js allows developers to subscribe to events and create filters. This feature is crucial for applications that require real-time updates from the Ethereum network.
  • JSON-RPC technique: Web3.js uses the JSON-RPC technique, or Remote Procedure Call, to enable communication between clients and the Ethereum blockchain.

Overall, Web3.js is highly important for Ethereum development, offering a range of functions that simplify and streamline the process of building blockchain-based applications.

How to Install Web3.js?

Here are the steps you need to follow to install Web3.js on your system:

  1. Pre-requisites

Before starting the installation process, ensure that Node.js is installed on your system.

Node.js is a runtime environment that lets you run JavaScript outside of a web browser. You can download it from the official Node.js website.

  1. Install Web3.js

Once Node.js is installed, you can proceed to install Web3.js. Open your command prompt or terminal and type the following command:

npm install web3 or yarn add web3

This command will install the latest version of Web3.js on your system.

  1. Verify the Installation

To confirm that Web3.js has been successfully installed, try importing it into a JavaScript file. You can do this by creating a new .js file in your preferred code editor, then adding the following line at the top:

const Web3 = require(‘web3’);

If you don’t encounter any errors when running this file, that means Web3.js has been installed correctly.

  1. Connect to an Ethereum Node

The final step is connecting to an Ethereum node. This can be done using a provider, which is a bridge between your application and the Ethereum network. You can create a new instance of Web3 with your provider as follows:

const web3 = new Web3(‘https://mainnet.infura.io/v3/YOUR-INFURA-PROJECT-ID’);

In the above line, replace ‘YOUR-INFURA-PROJECT-ID’ with your actual Infura project ID.

And there you have it! You’ve successfully installed Web3.js on your system and are ready to start building Ethereum applications.

Configuring Web3.js for Different Blockchain Networks

Configuring Web3.js for different blockchain networks is an essential step in utilizing its full potential. Web3.js provides the flexibility to connect to various blockchain networks, such as Ethereum, Binance Smart Chain, or Polkadot. It requires specifying the network’s endpoint URL, commonly known as the provider.

By configuring Web3.js with the appropriate provider, developers can interact with the desired blockchain network and perform transactions, deploy smart contracts, and access blockchain data.

Here’s a straightforward process to help you configure Web3.js for different blockchain networks:

Connecting to Local Ethereum Network (Ganache)

If you are testing your DApp locally, you can use Ganache as your personal blockchain network. To connect your Web3.js to Ganache, use the following code:

const Web3 = require(‘web3’);

const web3 = new Web3(‘http://localhost:7545’); // Ganache defaults to this port

Connecting to Public Ethereum Networks

For public Ethereum networks like Mainnet or Rinkeby, you will need to use an Ethereum node service like Infura. You can sign up on their website and get access to a URL for the network you want to connect to.

Here’s how you can connect to Rinkeby network using Infura:

const Web3 = require(‘web3’);

const web3 = new Web3(‘https://rinkeby.infura.io/v3/YOUR-INFURA-PROJECT-ID’);

Replace ‘YOUR-INFURA-PROJECT-ID’ with your actual Infura project ID.

Connecting to Binance Smart Chain

To connect to Binance Smart Chain, you can use the BSC’s public data seed node. The following code can be used to connect to its mainnet:

const Web3 = require(‘web3’);

const web3 = new Web3(‘https://bsc-dataseed.binance.org/’);

Linking Web3.js with Polkadot Network

Polkadot has its own JavaScript API, known as Polkadot-JS. This API is the standard way of connecting to the Polkadot network.

Still, if you want to stick to Web3.js for consistency or other reasons, you can do so by connecting to a Substrate-based chain that supports Ethereum compatibility layer, Moonbeam.

Connecting to Moonbeam via Web3.js

Moonbeam provides compatibility with Ethereum’s developer tools and network. It means you can use Web3.js to connect to Moonbeam nodes running on Polkadot or any Substrate-based chain.

Here’s how you can do it:

const Web3 = require(‘web3’);

const web3 = new Web3(‘https://rpc.testnet.moonbeam.network’);

In this code, we’ve connected to Moonbeam’s TestNet. Please replace the URL with the actual RPC endpoint of the network you are connecting to.

In these examples, we’ve connected to a few different networks, but the process is the same for any network you wish to connect to with Web3.js.

Remember to replace the provider URLs with the actual URL of the network you are connecting to.

Web3.js API Basics

At its core, the Web3.js API is an interface for Ethereum’s JSON RPC. It allows you to interact with a local or remote Ethereum node using HTTP, IPC, or WebSocket protocols.

The API offers multiple services, including sending transactions, calling smart contracts, querying blockchain data, and even subscribing to blockchain events.

Structure of the Web3.js Object

The Web3 object is the primary entry point for the Web3.js library. It’s an umbrella object that holds several modules, each providing specific functionality.

Here’s a simple breakdown:

  • web3.eth: This module contains functions for interacting directly with the Ethereum blockchain. It includes methods for sending transactions, interacting with smart contracts, and accessing blockchain data.
  • web3.utils: This utility module provides helper functions that you’ll find useful when developing DApps. These include functions for converting between different units of Ether, hashing data, and more.
  • web3.shh: This module is for Whisper protocol to communicate p2p and broadcast.
  • web3-eth-contract: This module allows you to interact with smart contracts on the Ethereum blockchain.
  • web3-eth-ens: ENS stands for Ethereum Name Service, which allows you to resolve human-readable names into Ethereum addresses.
  • web3-eth-abi: The ABI module is for encoding and decoding data to and from the Ethereum blockchain.
  • web3-eth-accounts: This module allows you to generate Ethereum accounts and sign transactions and data.
  • web3-bzz: The BZZ module is for interacting with Swarm, Ethereum’s decentralized file storage system.

By understanding these basics and exploring the different modules of the Web3.js API, you’re well on your way to developing robust and powerful DApps.

Smart Contracts and Web3.js

With Web3.js, you can interact with smart contracts on the Ethereum blockchain, deploying them, calling their functions, and listening for events they emit. This groundwork allows developers to craft decentralized applications that are transparent, secure, and operate without the need for intermediaries.

Here is the process of working with smart contracts using Web3.js:

Deploying a Smart Contract Using Web3.js

To deploy a smart contract, you need the contract’s ABI (Application Binary Interface) and its compiled bytecode.

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


data: bytecode,

arguments: [constructorArg1, constructorArg2, …]



from: ‘0xyourAddress’,

gas: 1500000,

gasPrice: ‘30000000000000’

}, (error, transactionHash) => { … })

.on(‘error’, (error) => { … })

.then((newContractInstance) => {



Interacting with a Smart Contract Using Web3.js

Once deployed, you can interact with the smart contract. For instance, to call a function named myFunction that is defined in your smart contract, you would do something like this:

contract.methods.myFunction(arg1, arg2, …)

.call({ from: ‘0xyourAddress’ }, (error, result) => { … });

Transactions with Web3.js

Transactions are a fundamental part of how blockchain works, enabling the transfer of assets and information from one account to another. With Web3.js, managing these transactions on the Ethereum network becomes streamlined and efficient.

Here, we will guide you through the process of creating, signing, and sending transactions, making sure you have the tools needed to move assets securely on the blockchain.

Whether you’re sending Ether, interacting with a smart contract, or deploying one, understanding transactions is key to building dynamic and functional DApps.

How to Create and Sign a Transaction Using Web3.js?

Creating and signing a transaction is an essential part of interacting with the Ethereum blockchain. Here’s a step-by-step guide on how to do it using Web3.js.

Creating a Transaction

First, you need to set up the transaction details. This includes the recipient’s address, the amount of Ether to send (in Wei), and the gas limit.

let tx = {

to: ‘0xrecipientAddress’,

value: web3.utils.toWei(‘0.1’, ‘ether’),

gas: 21000,


Signing the Transaction

Next, use your private key to sign the transaction. Remember, never expose your private key in your code or anywhere else.

// Import the account module from web3-eth-accounts

const Accounts = require(‘web3-eth-accounts’);

// Create an accounts object

const accounts = new Accounts(‘http://localhost:8545’);

// Sign the transaction

const signedTx = await accounts.signTransaction(tx, ‘0xyourPrivateKey’);

Sending the Transaction

Finally, you can send the signed transaction to the network.


.once(‘transactionHash’, (hash) => console.log(`Transaction hash: ${hash}`))

.on(‘error’, (error) => console.error(error));

Tracking Transaction Status

After sending the transaction, you can track its status.


.then(receipt => console.log(receipt))

.catch(error => console.error(error));

Events and Filters with Web3.js

In the world of blockchain development, particularly when working with Ethereum and its compatible chains, events are a critical component. They provide a way for smart contracts to communicate that something has happened to external listeners.

What Are Events?

Events in the context of Ethereum are pieces of code within a smart contract that execute when certain conditions are met. They’re essentially a logging system for the blockchain.

When an event is fired, it gets recorded into the transaction’s log, a data structure attached to each transaction on the Ethereum blockchain. This log is immutable, meaning once an event is recorded, it cannot be changed or erased.

Subscribing to Events and Creating Filters with Web3.js

Web3.js provides methods to listen for these events. The primary way to do this is through the `web3.eth.subscribe` function. This function allows you to listen for new block headers, pending transactions, and logs matching a filter.

Here’s a basic example:

web3.eth.subscribe(‘logs’, {

address: ‘0xcontractAddress’,

topics: [‘0xeventTopic’]

}, (error, result) => {

if (!error)



In this code snippet, we’re subscribing to logs from a specific contract address and a specific event topic. Whenever a new log entry is created that matches these criteria, our callback function will be called with the log entry as an argument.

Filters are a powerful tool for narrowing down the events you want to listen for. They allow you to specify the exact conditions that an event must meet to trigger your listener.

You can filter by contract address, event signature, and indexed event parameters.

Here’s an example of creating a filter for a specific event parameter:

web3.eth.subscribe(‘logs’, {

address: ‘0xcontractAddress’,

topics: [‘0xeventTopic’, null, ‘0xparameterValue’]

}, (error, result) => {

if (!error)



In this case, we’re listening for logs from a specific contract and event, where the third indexed parameter has a specific value.

Understanding how to work with events and filters is key to building effective dApps with Web3.js. They allow your application to react in real-time to changes on the blockchain, making your dApp more responsive and dynamic.

Web3.js with TypeScript: Benefits and Challenges

TypeScript is a popular programming language that extends JavaScript by adding types. When used with Web3.js for developing decentralized applications (DApps) on the Ethereum blockchain, it brings several advantages but also a few challenges.

Benefits of Using TypeScript with Web3.js

Strong Static Typing

TypeScript offers strong static typing, which can significantly improve code reliability. This feature can catch potential bugs at compile time, before the code is run. It’s especially beneficial in blockchain development where errors can lead to significant financial losses.

Enhanced Tooling

TypeScript provides superior tooling support with modern code editors like Visual Studio Code. Features like autocompletion, type inference, and automated refactoring can speed up the development process and reduce coding errors.

Improved Code Maintainability

With TypeScript, code maintainability is enhanced. The language’s features such as interfaces and types make the code more readable and easier to understand, which is crucial when working on large-scale projects or when collaborating with other developers.

Challenges of Using TypeScript with Web3.js

Learning Curve

While TypeScript is a superset of JavaScript, it introduces several new concepts and features that might be challenging for developers new to the language. Understanding these features and how to use them effectively can take time.

Compatibility Issues

Although Web3.js has TypeScript declaration files, they are not always up-to-date or complete. This could lead to some compatibility issues when trying to use certain Web3.js functionalities with TypeScript.

Web3.js Alternatives and When to Use Them

In the world of Ethereum development, Web3.js is a well-known library. However, there are other alternatives that developers can consider depending on their specific needs.

Here, we’ll discuss some of these alternatives and the circumstances where they might be more suitable.


Ethers.js is a popular alternative to Web3.js. It’s lightweight and offers broader blockchain network interoperability, enhanced performance, and native TypeScript support.

Ethers.js uses Promises for asynchronous code, making it more modern and readable compared to the callback-based API of Web3.js.

Use Ethers.js when:

  • You need a lightweight and performant library.
  • You’re working with TypeScript and want native support.
  • You prefer using Promises instead of callbacks for asynchronous code.


Blockdaemon is a blockchain infrastructure platform for node management. It’s not a direct replacement for Web3.js, but it can complement it by providing reliable and scalable node infrastructure.

Use Blockdaemon when:

  • You need to manage multiple nodes.
  • You require a scalable blockchain infrastructure.


Anyblock is another blockchain analytics platform. It provides access to indexed blockchain data for quick and accurate analytics.

Use Anyblock when:

  • You need quick and easy access to indexed blockchain data.
  • You’re carrying out blockchain analytics.

Coinbase Cloud

Coinbase Cloud is a suite of cloud-based services for building crypto applications. It includes APIs for sending transactions, retrieving blockchain data, and managing wallets.

Use Coinbase Cloud when:

  • You’re developing a crypto application and need various services.
  • You want a cloud-based solution for easier scalability and maintenance.


Sequence is a wallet-as-a-service platform. It provides APIs for integrating blockchain wallets into applications.

Use Sequence when:

  • You’re developing an application that requires wallet integration.
  • You want a managed service for handling wallet functionality.

Choosing between Web3.js and its alternatives depends on your specific needs and the nature of your project. While Web3.js is a robust library for Ethereum development, other libraries or platforms might offer features more suited to your use case.

Benefits of Web3.js in Web Development

One of the key benefits of Web3.js is that it allows developers to write smart contracts with minimal costs. Smart contracts are self-executing contracts with the terms of the agreement directly written into code. They are stored on the blockchain, making them transparent, traceable, and irreversible. (Here are some smart contracts platforms worth checking.)

Another significant advantage is its ability to create applications that leverage the decentralized nature of blockchain technology. Decentralization means that no single entity has control over the entire network, promoting transparency and reducing the risk of data tampering.

Moreover, Web3.js acts as a bridge between the Ethereum blockchain and JavaScript, one of the most widely used languages in web development. This compatibility makes it easier for developers already familiar with JavaScript to start creating decentralized applications.

With Web3.js, you get certified, authentic responses directly from a blockchain. This eliminates the need to trust any third party, enhancing data security and integrity.

Web3.js enables developers to fulfill their responsibilities in developing clients that interact with the Ethereum blockchain. In essence, it simplifies the process of integrating blockchain technology into web applications, making it an essential tool in the modern web developer’s toolkit.

Common Issues with Web3.js and How to Troubleshoot Them

Here, are some common issues faced when using Web3.js and their practical solutions:

  1. Transaction Failures

Transactions might fail due to a variety of reasons, such as insufficient gas fees or contract errors. To troubleshoot this, closely examine the transaction history and check the gas fees. Also, review your smart contract for any potential errors.

  1. ‘jsonrpcprovider’ Property Error

The ‘jsonrpcprovider’ property is part of the Web3 library. If you encounter an error related to this, it might be due to improper setup. Ensure that this property is correctly set up within your application.

  1. Compatibility Issues with TypeScript

While Web3.js does have TypeScript declaration files, they may not always be up-to-date. If you’re encountering compatibility issues, consider checking whether the declaration files are current and complete.

  1. Security Risks

Web3.js, like any other web-based technology, is prone to security risks. These might include lack of encryption and verification for API queries or risks associated with smart contracts. Regular audits and careful coding practices can help mitigate these risks.

  1. Calling a Contract Incorrectly

If there’s an error when calling a contract with Web3.js, it might be due to incorrect usage. Always double-check your code against the Web3.js documentation to ensure that you’re calling the contract correctly.

  1. Scalability and Adoption Issues

Web3 developers often face scalability and adoption issues. While these are more complex and not specific to Web3.js, staying up-to-date with the latest developments in the field and adopting best practices can help.

Examples of Web3.js Applications

Web3.js, a library enabling web applications to interact with the Ethereum blockchain, has been instrumental in creating numerous real-world applications. These applications span various sectors and demonstrate the versatility and benefits of Web3.js.

One notable application is Polkadot, a multi-chain platform that enables the transfer of any type of data or asset across different blockchains.

Using Web3.js, Polkadot can facilitate interoperability between diverse networks. This capability makes it possible to build applications on Polkadot that leverage the unique advantages of different blockchains.

Another standout application is Axie Infinity, a blockchain-based game where players breed, raise, battle, and trade fantasy creatures called Axies. Through Web3.js, Axie Infinity integrates blockchain technology to enable true ownership of digital assets. Players can earn cryptocurrency rewards and sell their Axies on the marketplace, demonstrating a new model for digital economies.

Uniswap, a decentralized finance (DeFi) protocol, is another example of a real-world application built with Web3.js. Uniswap allows users to swap ERC20 tokens directly from their wallets in a permissionless and decentralized manner. Web3.js plays a crucial role in enabling the smart contracts that make such transactions possible.

These applications underline the potential of Web3.js in creating decentralized applications that are secure, transparent, and capable of disrupting traditional business models.

Would you like to build a decentralized application (dApp) using Web3.js? Hire Web 3.0 Developers from MXICoders to leverage our expertise in blockchain technology and web development.


In conclusion, Web3.js is a powerful JavaScript library that allows developers to interact with blockchain technologies and build decentralized applications. Its significance lies in revolutionizing web development by enabling the integration of blockchain features, such as smart contracts and decentralized finance.

To further explore and learn about Web3.js, developers can refer to the official documentation and online tutorials available on the Ethereum website and other reputable resources in the blockchain development community.


By Ashok Rathod

Life is all about solving problems. Ashok is a software developer, technology enthusiast, founder, and director of a reputed software development company. Eager to help brilliant minds, and entrepreneurs with MVP ( Minimum Viable Product ) development, and technology consultation. Ashok is an engineer, a strategist, an investor, an architect, and a blogger who love to share about technology.

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