How to Build a Web Performance Monitoring CLI with Node.js and Lighthouse

How to Build a Web Performance Monitoring CLI with Node.js and Lighthouse Web performance directly impacts user experience, SEO rankings, and conversion rates. Yet most developers only check performance manually through Chrome DevTools or PageSpeed Insights — reactive, inconsistent, and easy to forget. What if you could monitor any website's performance metrics from your terminal, automatically, on every deploy? In this tutorial, we'll build a CLI tool that runs Lighthouse audits programmatically, tracks Core Web Vitals over time, and alerts you when performance degrades. You'll learn how to use Lighthouse's Node.js API, store historical metrics, and build a practical developer tool from scratch. What We're Building Our CLI — perfwatch — will: Run Lighthouse audits on any URL from the terminal Extract Core Web Vitals (LCP, FID, CLS, FCP, TTFB) Store results in a local JSON history file Compare current results against baselines and previous runs Output a clean, color-coded terminal repo