# Core Web Vitals for Ecommerce > Understand LCP, INP, and CLS, diagnose weak results and improve real customer page experience without chasing one lab score. - Type: Merchant guide - Level: Intermediate - Reading time: About 7 minutes - Audience: Written for store owners, builders, and designers refining high-performance ecommerce stores. - Last updated: 2026-11-04 - Canonical page: https://academy.getzenbasket.com/merchant-questions/core-web-vitals-for-ecommerce/ - Part of: [Merchant Questions](https://academy.getzenbasket.com/merchant-questions/) on ZenBasket Academy --- ## What you need to know ### What are Core Web Vitals? Core Web Vitals are Google's page-experience measures for loading, responsiveness and visual stability. The current metrics are Largest Contentful Paint, Interaction to Next Paint, and Cumulative Layout Shift. ### What is Largest Contentful Paint (LCP)? Largest Contentful Paint measures how long it takes the largest visible content element to render. On a product page, that element is often the main product image or a large heading block. ### What is Interaction to Next Paint (INP)? Interaction to Next Paint measures how quickly the page gives visual feedback after customer interactions across a visit. Long JavaScript tasks commonly delay the response to taps, typing, or selections. ### What is Cumulative Layout Shift (CLS)? Cumulative Layout Shift measures unexpected movement of visible page content. A product image, banner or review block that appears without reserved space can push an Add to Cart button away as a shopper taps it. ### Why is my LCP poor? LCP is often poor when the server responds slowly, the main image is too large or discovered late, or styles and scripts delay rendering. Identify the actual LCP element on each page type before optimizing it. ### Why is my INP poor? INP is often poor when large JavaScript tasks block the browser, or an interaction triggers too much rendering and data work. Record a slow interaction and trace the event handler, main-thread work and updated page area. ### Why is my CLS poor? CLS is often poor when images and ads lack reserved dimensions, fonts change text size or content is inserted above existing controls. Reserve space and avoid moving content after the shopper begins using the page. ### How do I improve Core Web Vitals on an ecommerce site? Improve the weakest metric by page type: speed the LCP resource, reduce interaction-blocking work and reserve space for late content. Confirm the change in lab tests, then wait for enough real-user data to judge the customer result. ### A quick store check Review LCP, INP and CLS at the 75th percentile by page type and device, then reproduce the weakest result in a controlled test. --- ## Frequently asked questions ### Do Core Web Vitals measure checkout success? No. They measure important page-experience qualities; track checkout errors and completion separately as business metrics. ### Can a page pass in the lab and fail for customers? Yes. Real devices, networks, locations and interactions can expose problems a single lab run misses. --- ## Related learning path - **How Ecommerce Pages Load** - **Ecommerce Image and Video Performance** - **Ecommerce Speed and JavaScript SEO** - [ZenBasket Build Guide](https://help.getzenbasket.com/zenbasket-builder/)