Shopify Core Web Vitals: Why Your Store Is Slowing Down & How to Fix It (2025)

When most merchants talk about "speeding up" a Shopify store, they think about loading time in general. Google, however, measures that experience through a stricter lens: Core Web Vitals. If your LCP, CLS, or INP metrics are poor, your store can feel slow and unstable even if the overall load time doesn't look terrible.

This article focuses specifically on Shopify Core Web Vitals—why your scores often drop over time, what's really slowing you down, and how to fix the underlying issues without rebuilding your store from scratch. If you want a broader speed checklist later, you can pair this guide with our full slow Shopify store checklist.

1. Why Shopify Core Web Vitals matter

Core Web Vitals are Google's way of measuring real user experience. For Shopify merchants, that translates directly into money. A store that feels instant and stable is easier to shop from; a store that janks, jumps, or hesitates quietly kills conversion rate.

• Higher organic rankings: Core Web Vitals are part of Google's page experience signals. While they're not the only ranking factor, consistently poor metrics can hold back your SEO.
• Better paid traffic results: Fast, stable landing pages help improve Quality Score in Google Ads and performance in Meta campaigns, which can lower your cost per click and per purchase.
• More completed checkouts: Shoppers are less likely to abandon a smooth, predictable experience. Slow product pages and jumpy carts cause subtle friction at every step.
• Stronger brand perception: A snappy store feels modern and trustworthy; a sluggish one feels outdated, even if your design looks good.

The tricky part? You can have a beautiful, high-converting Shopify theme at launch, then watch performance degrade over time as you add apps, scripts, and content. That's usually when Core Web Vitals warnings start showing up.

2. Quick checks to confirm your Shopify store is slow

Before you start uninstalling apps or editing your theme, it's worth confirming with data that your store really has a Core Web Vitals problem. These quick checks take less than 10 minutes.

• Run PageSpeed Insights on key templates: Test your homepage, a best-selling product page, and a high-traffic collection. Focus on the mobile report and the Core Web Vitals section.
• Check the "Origin summary" tab: If Google has enough field data, you'll see how real visitors experience LCP, CLS, and INP — not just lab scores.
• Open your store on 4G: Use your phone on a cellular network with no Wi-Fi. If the page feels heavy or jerky to you, it's likely worse for shoppers on mid-range devices.
• Watch for layout shifts: Pay attention to buttons or text that unexpectedly move as images, banners, or apps finish loading. That's CLS in action.
• Test a simple page vs a "marketing-heavy" one: Compare a bare-bones page with few apps to a campaign landing page with pop-ups, tracking pixels, and media. The difference usually reveals where your biggest problems sit.

If your mobile scores are orange or red, or if the Core Web Vitals field data shows "Needs improvement" or "Poor", it's time to treat Shopify performance optimization as a priority, not a nice-to-have.

3. How Core Web Vitals work on Shopify (LCP, CLS, INP)

Core Web Vitals aren't random numbers — each metric describes a specific moment in your shopper's journey. Understanding them makes it much easier to fix them.

A strong Shopify Core Web Vitals fix focuses on all three metrics together. Speeding up LCP but ignoring CLS and INP still leaves users with a clunky experience and can hurt your long-term SEO.

4. Pre-optimization Core Web Vitals audit checklist

Before you start removing apps or rewriting sections, capture a baseline. That way, you'll know what actually moved the needle. This small audit mirrors what we do at FASTRANK before any Shopify speed optimization service.

5. Full checklist to fix Shopify Core Web Vitals (2025)

This is the same framework we use when we help clients move from red to green Core Web Vitals scores on Shopify. You can follow it yourself or treat it as a blueprint for your developer or agency. If you want a broader view that also covers hosting and long-term maintenance, pair this guide with our Shopify Speed Optimization Guide (2025).

5.1 Remove or replace performance-killing apps

Apps are the number one reason Shopify stores become slow. Every app can add scripts, styles, external requests, and hidden DOM elements — often on every page, not just where you use the feature.

• Uninstall anything you no longer use: If an app isn't actively contributing to sales or workflows, remove it completely instead of leaving it "just in case".
• Consolidate overlapping functionality: Replace several single-purpose widgets (badges, pop-ups, timers) with one lightweight solution.
• Prefer apps that load selectively: Look for tools that only inject scripts on specific templates instead of site-wide.
• Clean up leftover code: Even after you delete an app, snippets may remain in theme.liquid or section files. If you're comfortable with Liquid, remove orphaned includes and script tags carefully.

For a deeper breakdown of which tools tend to cause bloat, see our upcoming analysis: Best Shopify Apps That Slow Down Your Store (2025).

5.2 Fix image-related LCP problems

Oversized, unoptimized images are one of the fastest ways to destroy LCP. The goal isn't to make your store ugly — it's to serve the same visual quality with far less weight.

• Compress hero and banner images so they stay under roughly 200KB whenever possible.
• Use WebP (or AVIF if supported by your stack) alongside fallbacks for older browsers.
• Resize product images to the largest size they're actually displayed at, rather than uploading 4000px versions.
• Lazy-load below-the-fold imagery so it only loads when a shopper scrolls down.
• Ensure your LCP image is requested early, with no unnecessary placeholders or blocking scripts in front of it.

5.3 Stabilize layout to fix CLS

Shopify themes tend to accumulate layout shifts as merchants add announcement bars, app widgets, and new sections. The objective here is to reserve space for everything that will appear, so nothing surprises the shopper.

• Set fixed heights where possible: Reserve space for hero images, slideshows, and home page banners.
• Pre-allocate areas for app content: For review widgets, badges, or upsell modules, give the container a minimum height so they don't suddenly push content down.
• Avoid inserting elements above existing content: If you add a new announcement bar or free-shipping strip, place it inside a reserved container rather than pushing the entire header down on load.
• Use system fonts or font-display strategies: Poor font loading can also contribute to CLS if large chunks of text suddenly re-render.

5.4 Improve INP by reducing JavaScript bloat

INP is heavily influenced by how much work your JavaScript has to do when somebody interacts with your store. The more you can trim, defer, or compartmentalize scripts, the more responsive everything will feel.

• Limit heavy sliders, carousels, and video backgrounds on mobile.
• Defer non-critical scripts so they run after the first paint instead of blocking user interaction.
• Load third-party scripts (analytics, chat, A/B testing) asynchronously where possible.
• Remove unused event listeners, abandoned tracking pixels, and old A/B test scripts that are no longer in use.

5.5 Use theme settings instead of extra apps

Modern Shopify themes ship with a surprising amount of built-in functionality: FAQs, color swatches, announcement bars, product tabs, and more. Using theme features instead of installing yet another app is an easy way to protect your Core Web Vitals.

Before browsing the app store, check whether your theme already offers what you're looking for. Many merchants install apps for features they technically had from day one.

5.6 Combine this with a broader optimization plan

Core Web Vitals don't exist in a vacuum. Hosting, CDN configuration, and caching also influence how quickly your Shopify store responds, especially for international audiences. For a bigger, strategic view of all the moving parts, you can follow the step-by-step process in our slow Shopify store checklist alongside this Core Web Vitals guide.

6. Testing after improvements

Once you've worked through a first pass of the checklist, repeat the tests you ran during your initial audit. Use the same URLs and tools so the comparison is fair.

• Re-run PageSpeed Insights on mobile and note the new LCP, CLS, and INP values.
• Check the Core Web Vitals field data again after a few weeks to see how real-world metrics respond.
• Compare your updated Shopify speed score with the baseline you recorded earlier.
• Keep an eye on business metrics: conversion rate, bounce rate, and cost per purchase from paid campaigns.

If you see strong lab improvements but field data stays poor, that usually means certain templates or countries are still under-optimized, or that a heavy app only loads for specific traffic sources.

7. When to hire a Shopify Core Web Vitals expert

Many of the steps above are safe to tackle yourself, especially if you're comfortable experimenting on a duplicate theme. But there are cases where bringing in a specialist saves a lot of time, stress, and lost revenue.

Consider expert help if:

• Your store is a major revenue channel and you can't risk breaking the live theme.
• You rely on several mission-critical apps (subscriptions, bundles, reviews) that need careful coordination.
• Your current theme has years of custom code layered on top of it.
• You've tried "one-click" optimization apps but Core Web Vitals are still poor.
• You want a structured, report-driven approach rather than trial and error.

A good Shopify speed optimization agency will start with a clear audit, explain what's actually slowing you down, and then implement fixes with backups and staging in place. They'll also show before/after metrics, not just say "we turned on a setting in an app".

8. How this guide connects to other Shopify speed resources

This article zooms in on Core Web Vitals, but it's part of a larger Shopify performance playbook. For a complete picture, you can read it alongside:

• How to Fix a Slow Shopify Store — Full Checklist (2025) — practical, step-by-step tasks that go beyond Web Vitals alone.
• Shopify Speed Optimization Guide (2025) — a higher-level roadmap from audit to implementation and monitoring.
• Before/After Shopify Speed Optimization — Case Study — a real-world example of how these principles play out on a live store.

If you also run a WordPress or WooCommerce site alongside Shopify, you can apply the same thinking there using our WordPress Speed Optimization Guide (2025). The stack is different, but the Core Web Vitals logic is the same.

9. How to get started improving Shopify Core Web Vitals

You don't need to become a performance engineer to make meaningful improvements. Start small, be methodical, and treat this guide as a living checklist rather than a one-off project.

• Run your initial audits and save screenshots of your scores.
• Clean up apps and images first — they usually give the fastest wins.
• Move on to layout stability and JavaScript bloat to unlock better CLS and INP.
• Re-test regularly and keep an eye on both Core Web Vitals and business metrics.

And if you'd rather hand the heavy lifting to a team that lives and breathes this stuff, our specialists at FASTRANK offer done-for-you Shopify site speed optimization with a clear process, transparent pricing, and detailed before/after reporting.