Why is my Shopify store slow? A Core Web Vitals troubleshooting guide

A Shopify store is usually slow for one of three reasons: a large or late-loading hero image (Largest Contentful Paint), too much app and theme JavaScript (Interaction to Next Paint), or images, banners and app widgets that push content around as they load (Cumulative Layout Shift). To find which one, work through six steps: decide which number to trust, find the failing metric and template, check what changed, apply the fix for that metric, test it on a duplicate theme, then re-measure once real visitor data has caught up.

Speed numbers disagree because they measure different things. A lab test loads one page once, on a simulated device and connection. Field data records what real visitors experienced over weeks. Field data tells you whether there is a problem; lab tools help you find the cause.

Shopify's Web performance dashboard summarises real user data from the past 30 days at the 75th percentile. Shopify notes that data might be delayed by up to 36 hours, that it keeps 90 days of data, and that a new store or one in private mode (password-protected) might not have metrics at all.

Google's thresholds for a good experience are measured at the 75th percentile of page loads, segmented across mobile and desktop. Shopify's dashboard uses the same "good" lines and adds its own moderate and poor bands.

Then open the Page Type report for the failing metric. Shopify describes it as a way to see whether certain page templates affect performance. A store whose product pages fail INP while the home page passes has a product page problem, usually an app that only loads there.

Speed rarely drops for no reason. On the dashboard's Over Time charts, Shopify shows event annotations as numbered vertical lines; hovering over one shows changes such as app installations, theme updates and new code. Line those up against the date the metric moved.

Annotations won't catch everything, so check the usual suspects as well.

LCP. On Shopify this is most often a large hero image or a render-blocking script delaying everything behind it. Serve the hero at the size it displays, don't lazy-load the image that is the largest element, avoid sliders and video as the main above-the-fold element where possible, and move scripts that aren't needed for first paint out of the way.

INP. This is almost always a JavaScript problem, and apps are the most common source. Find which apps load scripts on every page rather than only where needed, and remove or defer anything not earning its cost. Our app audit checklist covers this step in detail. Tag managers carrying many tags have the same effect.

CLS. Give images, embeds and app content explicit dimensions or reserved space so the layout doesn't jump as they load. Late-injected banners, cookie bars and review widgets are common causes.

Never test speed fixes on the live theme. Duplicate it, make one change at a time, and compare the same templates in a lab tool before and after. To see what an app costs before you uninstall it, use the request blocking feature in Chrome DevTools to block its script on the duplicate theme's preview and re-run the test.

If the slowness looks like server time rather than scripts, the Shopify Theme Inspector for Chrome shows Liquid render profiling as a flame graph, which helps find theme code that is slow to render. Check that apps, tracking and checkout still work on the duplicate before publishing it.

Once the fix is live, give field data time. Shopify's dashboard can lag by up to 36 hours, and its summary covers the past 30 days, so the headline figure moves slowly. Use the Over Time report to see whether the line changes after your publish date, and re-check the Page Type report for the template you fixed.

Write down the date and what you changed, so the next annotation on the chart has an explanation.

Hypothetical example: a homeware store's dashboard shows INP moving from good to moderate on mobile. The Page Type report shows product pages are the problem; collection and home pages are fine. An annotation two weeks earlier marks an app installation: a product personalisation widget. On a duplicate theme, blocking the widget's script brings lab interaction times back down. The team limits the widget to the products that use it, publishes, and watches the Over Time chart for the following weeks.

Shopify has published its own analysis: for every 100 milliseconds slower a store loads, measured by LCP, conversion tends to be about 3.5% lower. This is vendor data from Shopify, based on a 28-day window around January and February 2026, and Shopify describes it as correlation, not direct causation. Treat it as a reason to take speed seriously, not as a forecast for your store.

For how performance connects to conversion and what to prioritise for revenue, see our guide to how site speed affects Shopify conversion rates.

This flow assumes an Online Store theme. Headless storefronts built with Hydrogen or another framework need the developer's own monitoring. Checkout isn't built from your theme's templates, so this flow doesn't diagnose checkout speed. If your site isn't on Shopify at all, use our general guide to diagnosing a slow website instead.

Some fixes also have business costs: removing a reviews widget or a personalisation app may speed up a page and still lose sales. Decide those with conversion data, not speed data alone.

web.dev: Web Vitals; Shopify Help Center: Web performance dashboard; Shopify.dev: Shopify Theme Inspector for Chrome; Shopify: store speed and conversion (published 27 April 2026, vendor data).

Accessed 14 October 2026. Dashboard features and reporting windows can change; check Shopify's current documentation.

Performance degrades gradually as apps and content are added, so a single optimisation pass doesn't hold. Make the six steps part of your regular maintenance routine: check the dashboard monthly, log every change, and test new apps on a duplicate theme before they go live. Performance matters most on mobile; see our Shopify mobile CRO guide for how it connects to conversion there. If fixes need theme or app work, that falls under Shopify development.