A practical guide to Shopify Core Web Vitals

Scores are a symptom

Core Web Vitals measure loading, visual stability and responsiveness. On Shopify, poor scores usually come from apps, images and a theme that loads everything at once. They rarely come from Liquid itself.

Fix the causes in an order that also helps conversion. A perfect lab score with a confusing product page is not a win.

Apps and scripts

Each app can add JavaScript to every page, including pages that do not use it. List what is installed, what it earns, and what it loads. Remove the ones that are idle.

Chat widgets, pop-ups and review apps are the frequent offenders. Keep the ones that pay, and load them after the page is usable.

Images

Serve the size the layout needs. A 3000 pixel photo in a 400 pixel card costs everyone on a phone. Use modern formats, set width and height so the page does not jump, and do not lazy-load the first image people see.

Theme weight

A custom or carefully edited theme should load one set of styles and the scripts the page uses. Carousels, animation libraries and icon fonts that you do not use should not be in the theme.

Online Store 2.0 sections help here: you can keep optional features out of templates that do not need them.

How to check

Use Search Console's Core Web Vitals report for field data, and a lab tool to find the script or image responsible. Field data is what your customers felt. Lab data is how you find the cause.

Retest after each change. If you change five things and the score moves, you will not know which one mattered.