Core Web Vitals are three measurements Google uses to describe how a page feels to a real visitor. For an online store they matter twice: slow product pages lose shoppers, and page experience is one of many signals used in search.
The three measurements
- Largest Contentful Paint (LCP) is how long the main content takes to appear. Google considers 2.5 seconds or less good.
- Interaction to Next Paint (INP) is how quickly the page responds when someone taps or clicks. Good is 200 milliseconds or less.
- Cumulative Layout Shift (CLS) is how much the page jumps around while loading. Good is 0.1 or less.
Measure first
Run your home page, a collection page, a product page and the cart through PageSpeed Insights, on mobile. In Google Search Console, the Core Web Vitals report shows how real visitors experience your site over time. Fix what the data shows, not what you assume.
What to fix, in order
- Images. Oversized images are the most common cause of a slow LCP. Serve them at the size they are displayed, in a modern format such as WebP, and do not lazy-load the main image at the top of the page.
- Apps and plugins. Every app or plugin can add scripts. Remove the ones you do not use, and check what each remaining one costs in loading time.
- Layout shifts. Give images, banners and embeds a fixed space before they load, so the page does not jump. Load fonts in a way that avoids sudden text changes.
- JavaScript. Delay or remove scripts that are not needed for the first screen. Heavy sliders and pop-ups are common offenders and often hurt INP.
- Hosting and caching. A slow server hurts everything. Use a good host and make sure caching is set up correctly.
Do not chase a perfect score
The goal is a store that feels quick on a mid-range phone on a normal connection. A score of 100 is not necessary. Getting each measurement into the good range on your key pages is.
I offer a store audit that lists what is slowing your pages, in order of impact.