How to check Core Web Vitals for hundreds of URLs at once (API + code)

Google's PageSpeed Insights is great for auditing one page. But the moment

you want to track Core Web Vitals across a whole site — or every client site

you manage, or every page after a deploy — clicking through a web UI (or fighting

per-key rate limits) stops scaling.

Here's how to measure LCP, CLS, FCP and TTFB in bulk, in real Chromium, with