Pull Crypto Data from Ethereum with Web3.js: No APIs, Just Metamask

Picture made with Grok 3 via X.com

Cryptocurrency markets move fast, and having direct access to real-time price data from blockchain networks can unlock a world of possibilities for developers. I showed before some ways to retrieve historical crypto data using APIs, for example here:

Obtaining historical and real-time crypto data with very simple web programming

However, APIs change and might become inaccessible, among other problems. Then, imagine you could retrieve crypto prices straight from a source deep inside a blockchain network, with no intermediaries, no servers, no API calls, just pure client-side code accessing directly data from a network from a web browser.

This article explores how to achieve exactly that by using Web3.js and MetaMask, tapping into Ethereum’s Mainnet via Chainlink’s decentralized oracles. We’ll cover:

• Why client-side Ethereum apps make sense
• Setting up Web3.js and MetaMask
• Finding Chainlink price feed contracts
• Fetching price data directly from Ethereum
• Adding notifications for price alerts