Performance

Shopify Core Web Vitals: What LCP, INP and CLS Mean and How to Improve Them

Core Web Vitals are Google's measures of real-world page experience. They are not the only factor in rankings, but slow, unstable pages also cost you conversions. This guide explains each metric and the fixes that apply most often on Shopify.

By FlowCart Agency · · 8 min read

The three metrics and their targets

  • Largest Contentful Paint (LCP) measures how quickly the main content appears. Good is 2.5 seconds or less.
  • Interaction to Next Paint (INP) measures how responsive the page is to taps and clicks. Good is 200 milliseconds or less.
  • Cumulative Layout Shift (CLS) measures unexpected movement as the page loads. Good is 0.1 or less.

These are assessed on real-user (field) data at the 75th percentile, so most visitors need to have a good experience, not just the average one.

Improving LCP

  • Identify the LCP element, which is often the hero or main product image.
  • Serve that image at the right size and do not lazy-load it.
  • Give it high fetch priority and avoid render-blocking scripts and styles above it.
  • Remove slow or unneeded apps that delay the first paint.

Improving INP

  • Reduce the amount of JavaScript running on the page, especially third-party scripts.
  • Defer non-essential scripts such as chat widgets and trackers.
  • Break up long tasks and avoid heavy work on click handlers.
  • Audit apps: many affect responsiveness more than load time.

Improving CLS

  • Set width and height on images and videos so space is reserved.
  • Reserve space for banners, review widgets and other late-loading elements.
  • Load fonts in a way that avoids visible text jumps.
  • Avoid inserting content above existing content after load.

How to measure and track

  1. Check PageSpeed Insights for field data on your key URLs.
  2. Use the Core Web Vitals report in Search Console to see groups of affected pages.
  3. Fix the worst templates first: usually product and collection pages.
  4. Recheck after changes. Field data takes a few weeks to reflect improvements.

More practical steps in our guide to speeding up your store without changing themes, and our Core Web Vitals service.

Frequently asked questions

What are good Core Web Vitals scores?
LCP of 2.5 seconds or less, INP of 200 milliseconds or less and CLS of 0.1 or less, measured at the 75th percentile of real-user data.
Do Core Web Vitals affect Shopify SEO?
They are part of Google's page experience signals, and they also affect conversion. They are one factor among many, so content and relevance still matter most.
Why is my Shopify INP high?
Usually because of heavy JavaScript, often from third-party scripts and apps. Reducing or deferring them typically helps most.

Keep reading