Build a Multi-Chain Crypto Wallet Monitor in Node.js (15 minutes)

trdevlin — Sat, 05 Sep 2026 18:05:58 +0000

Want to watch your crypto wallets across Ethereum, Base, Polygon, Arbitrum, and Optimism without signing up for anything? Here's the shortest path.

The one dependency

npm install wallet-watcher

const { getBalances } = require("wallet-watcher");
const balances = await getBalances("0xYourWallet");
// { eth: {symbol:"ETH", balance: 1.23}, base: {...}, polygon: {...}, ... }

No Alchemy key, no Infura signup, no web3 SDK. Public RPCs, one call,
five chains (BTC addresses work too).

Turn it into a monitor

Wrap it in a loop, diff the result, and you have a watcher:

setInterval(async () => {
  const now = await getBalances(WALLET);
  for (const [chain, info] of Object.entries(now)) {
    if (prev[chain] && prev[chain].balance !== info.balance)
      console.log(`🔔 ${chain}: ${prev[chain].balance} → ${info.balance}`);
  }
  prev = now;
}, 5 * 60 * 1000);

Turn it into a trading-bot base

I open-sourced a starter template that wires this into a clean loop with a
strategy file you own: crypto-bot-starter.
Edit strategy.js, plug in Telegram alerts, done.

When you actually need to swap

If you're moving between tokens, swapdeck.net is a
minimal no-signup swap UI for the same chains — connect and swap, no account.

Why this stack