Introduction
PageSpeed Insights is free. It is official. For one URL, right now, it is often the right tool.
You paste a link. You wait. You get a Lighthouse performance score, lab timings, and field Core Web Vitals when Google has enough Chrome visits. That is a strong snapshot.
A snapshot is not a watchman.
This guide is for people who ship websites and still live in PageSpeed tabs. It says when that habit is fine, when it starts to fail you, and what to add without turning every check into a science project.
