Page speed advice hasn’t changed much in years, but what actually correlates with conversion has. Here’s what we prioritize on every build. Core Web Vitals get treated as an SEO checkbox, and that undersells them. In our experience building and auditing e-commerce and lead-gen sites, the metrics that Google measures for ranking are often the same ones that quietly determine whether a visitor completes a purchase or bounces before they ever see your offer.
Largest Contentful Paint gets the most attention, and rightly so — but the fix isn’t always “compress your images.” Often the real culprit is a render-blocking script loaded in the head, or a web font that delays text from appearing at all. We’ve seen LCP improve significantly just from moving one third-party script to load after the main content, with zero changes to the images themselves.
Interaction to Next Paint, which replaced First Input Delay as a Core Web Vital, matters more than people assume on mobile commerce. A product page that looks fast but takes 400 milliseconds to respond to an “Add to Cart” tap feels broken to a user, even if nothing actually failed. We test this on real mid-range Android devices, not just a fast office laptop, because that’s where the gap usually hides.
The pattern we keep seeing: sites don’t need a rebuild to fix these numbers. They need someone to actually profile the page instead of guessing. That’s most of the work.