How to Swap Tokens Programmatically with TypeScript

Swapping tokens programmatically with TypeScript requires three things: a swap API that returns executable calldata, a wallet library to sign transactions, and an RPC connection to broadcast them. With DEX aggregators handling over $13.5 billion in daily trading volume and TypeScript dominating web3 frontend and bot development, knowing how to execute on-chain swaps from code is a core skill for any DeFi developer. This guide walks you through swapping tokens on any EVM chain using TypeScript and a free API that requires no key and no SDK — just a single GET request. What You'll Need Node.js 18+ or Bun (for native fetch) TypeScript (5.x recommended) viem or ethers.js for signing and sending transactions A wallet with a private key (testnet or mainnet) No API key — the swap API used in this guide is free and requires no registration Install the dependencies: npm install viem typescript Step 1: Fetch a Swap Quote The swap API at api.swapapi.dev takes a GET request with five parameters an