Performance

Google Lighthouse

Google Lighthouse is an open-source automated auditing tool built into Chrome DevTools that generates performance, accessibility, best practices, and SEO scores (0–100) for any URL. It measures lab performance metrics including Core Web Vitals, plus provides actionable recommendations.

Why It Matters for Shopify Stores

Lighthouse is the underlying engine behind Google PageSpeed Insights and Shopify's built-in speed report. Understanding Lighthouse helps merchants interpret the diagnostics and prioritize fixes by estimated impact. The 'Opportunities' section shows what can be improved with the biggest performance impact; 'Diagnostics' shows additional issues. Note that Lighthouse scores reflect simulated lab conditions — real-user field data in CrUX may differ.

How to Check Your Store

Open Chrome DevTools (F12) > Lighthouse tab. Select 'Mobile' mode and run an audit on your store. Or use pagespeed.web.dev for the same data without opening DevTools.

Use the free shopify speed test tool

How to Fix It

Follow the opportunities with the highest estimated savings first. Common high-impact opportunities for Shopify: render-blocking resources, properly sizing images, eliminating unused JavaScript.

Related Terms

Google PageSpeed Insights

Performance

Google PageSpeed Insights (PSI) is a free tool at pagespeed.

LCP (Largest Contentful Paint)

Core Web Vitals

Largest Contentful Paint measures how long it takes for the largest visible content element on a page — usually a hero image or headline — to finish loading.

CLS (Cumulative Layout Shift)

Core Web Vitals

Cumulative Layout Shift measures visual instability — how much page elements unexpectedly move while the page is loading.

INP (Interaction to Next Paint)

Core Web Vitals

Interaction to Next Paint measures the responsiveness of your page to user interactions — clicks, taps, and keyboard input.

Core Web Vitals

Core Web Vitals

Core Web Vitals are Google's set of user experience metrics that measure loading performance (LCP), visual stability (CLS), and interactivity (INP).

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