Web3.js
Web3.js is the original and most widely-used JavaScript library for interacting with the Ethereum blockchain and any Ethereum Virtual Machine (EVM)-compatible chain (Polygon, BSC, Base, Arbitrum, and others) from a web or Node.js application. It wraps the JSON-RPC calls that a blockchain node exposes into a friendlier JavaScript API for reading on-chain data (account balances, transaction history, smart contract state), sending transactions, and calling smart contract functions once a contract's ABI (interface definition) is provided.
Because Web3.js only talks to whatever RPC endpoint it's configured with, it doesn't run a blockchain node itself — in practice this means pairing it with a node provider like Infura, Alchemy, or Ankr (or a self-run node) to actually reach the network. Wallet connection for browser dApps (MetaMask and similar) integrates through the injected `window.ethereum` provider, which Web3.js wraps for signing transactions on the user's behalf without ever handling their private key directly.
For Nigerian developers building on the growing West African Web3/crypto ecosystem — remittance rails, tokenized savings products, or NFT marketplaces — Web3.js remains a common choice for smart contract interaction, though many newer projects now reach for ethers.js or viem instead for a smaller bundle size and more modern TypeScript-first API; Web3.js's main advantage is its maturity and the sheer volume of existing tutorials, Stack Overflow answers, and example code built around it.