Core Web Vitals are Google’s measures of how a page feels to use. They come from real visits in Chrome, so they reflect your customers’ phones and connections, not a test in an office.
The three numbers
- Largest Contentful Paint (LCP) measures loading: how long the biggest element on screen takes to appear. Good is 2.5 seconds or less.
- Interaction to Next Paint (INP) measures responsiveness: how quickly the page reacts when someone taps. Good is 200 milliseconds or less.
- Cumulative Layout Shift (CLS) measures stability: how much the page jumps around as it loads. Good is 0.1 or less.
Google judges each one at the 75th percentile of visits, so most of your visitors need a good experience, not just the ones on fast Wi-Fi.
Where to look
Use the field data at the top of PageSpeed Insights and the Core Web Vitals report in Search Console. The Lighthouse score underneath is a lab test. It’s useful for finding causes, but it isn’t what Google uses.
Fix LCP first
On most Shopify stores the largest element is the hero image or the first product photo.
- Never lazy-load the first image on the page.
- Serve images at the size they’re shown, using the width and srcset options in Shopify’s image filters.
- Replace autoplaying hero sliders with one strong image.
Then INP
Slow taps almost always come from too much JavaScript, and most apps that add storefront features add a script.
- List your apps and remove the ones you no longer use.
- Load chat widgets and pop-ups after the page is ready, or only when someone needs them.
- Check the theme for code left behind by apps you’ve already uninstalled.
Finally CLS
Give images a width and height so the browser reserves their space. Make sure announcement bars, review stars and app widgets don’t push content down when they load, and pick fallback fonts close in size to your brand font.
Measure, then wait
Field data covers the previous 28 days, so improvements take a few weeks to show in full. Change one thing at a time so you know what worked.