Shopify Store Slow? How to Find the Cause

Description

Troubleshooting Shopify store slow? How to find the cause

Shopify hosts the store, runs the CDN and optimises images for you, so the causes you can act on are the theme, the installed apps and third-party scripts. Read the real-visitor numbers in Shopify's web performance report first, find the date they got worse, then test apps and scripts on a duplicate theme. Clearing apps, tags and heavy sections is your job; theme code and Liquid fixes need a developer.

Get a technical assessment Last updated 2 October 2026

What can and cannot be the cause

On a Shopify store, several of the usual reasons for a slow website are already taken care of. Shopify's help centre lists what it handles automatically: hosting on global servers, a CDN run by Cloudflare, image optimisation through its image CDN, and minified CSS and JavaScript. You cannot change any of these, and they are rarely where the time goes.

Shopify names three things that do affect performance:

the theme

the apps you have installed

third-party code you have added by hand, including tag managers and the tags inside them

The diagnosis below works through those three. For websites that are not on Shopify, where hosting and caching are in play, the general guide is why is my website slow .

Step 1: Read the real-visitor numbers

Start in your Shopify admin, not with a speed-test site. Go to Online Store, then Themes, for the summary, and to Analytics, then Reports, for the full web performance reports.

The reports show three Core Web Vitals, measured from real visitors and reported at the 75th percentile.

Metric

What it measures

Good

Moderate

Poor

Largest Contentful Paint (LCP)

Loading speed

Up to 2.5 s

2.5 to 4 s

Over 4 s

Interaction to Next Paint (INP)

Response to taps and clicks

Up to 200 ms

200 to 500 ms

Over 500 ms

Cumulative Layout Shift (CLS)

Visual stability

Up to 0.1

0.1 to 0.25

0.25 or more

Three things to do here:

Filter by device type and read mobile on its own.

Write down which metric is failing. A poor LCP, a poor INP and a poor CLS have different causes and different fixes.

Remember the limits of the data: it covers the last 90 days only and can be delayed by up to 36 hours.

If all three are good on mobile, the store is not slow for most visitors, whatever a score elsewhere says.

Step 2: Cross-check with PageSpeed Insights

Run Google's PageSpeed Insights on three URLs: the home page, a busy collection and a typical product page. It returns two kinds of data.

Field data comes from the Chrome User Experience Report and covers real users over the previous 28 days, again at the 75th percentile. It should broadly agree with Shopify's report.

Lab data is collected in a controlled environment. Google describes it as useful for debugging. This is where the performance score comes from: 90 or above is good, 50 to 89 needs improvement, below 50 is poor.

Use the lab report for its list of what the page loaded and what blocked it. Do not treat the score as the goal. For scale, Shopify asks Theme Store themes for a minimum average Lighthouse performance score of 60 across the home, product and collection pages.

Step 3: Find the date it got slower

Go back to Shopify's report and look at the chart over time. It carries event markers, shown as numbered vertical lines, for app installations, theme updates and new code.

If a metric worsens just after a marker, you have a suspect. Test that change first. If the decline is gradual with no single event, the cause is more likely accumulation: one more app, one more section, one more tag, month after month.

Step 4: Test apps on a duplicate theme

Never test on the live theme.

In Online Store, open the actions menu on the live theme and choose Duplicate. A store can hold up to 20 themes, so delete an old copy if you are at the limit.

Open the duplicate in the theme editor and go to App embeds. App embeds are app elements that float over the page or add code without being visible.

Switch the embeds off one at a time, save, and preview the duplicate.

Run Lighthouse from Chrome's developer tools on the preview after each change and note the difference.

List every installed app and ask what it earns. Shopify's own advice is to evaluate apps and third-party code to make sure they create enough value.

Then look for apps that are gone but not gone. Shopify states that some apps add code to the theme that is not removed automatically when the app is uninstalled. If the store has had many apps over the years, expect leftovers.

Step 5: Audit tags and pixels

Open your tag manager and list every tag. For each one, name the tool it feeds and the person who looks at that tool. Remove the tags nobody can account for. Shopify's guidance says the same: audit the tag manager and remove unused or low-value tags.

Step 6: Check what the pages carry

These come straight from Shopify's performance guidance and need no code:

Sections. Avoid adding too many sections to a page template. Count the ones on the home page.

Images. Upload images at an appropriate size and in a recommended format.

Animations. If the theme offers page transitions or other animations, compare the numbers with them on and off.

Large collections. Turn on pagination for collections with many products.

Step 7: Profile the theme code

This step needs a developer. Shopify's Theme Inspector for Chrome draws a flame graph of how long each part of the theme's Liquid takes to render on the server, which shows the code that delays the page before anything reaches the browser. It works on stores the developer owns or has collaborator access to.

Shopify's developer guidance lists the faults to look for: loops nested inside loops, metafield lookups inside loops, a main image that is lazy-loaded or set as a CSS background, fade-in animations on the main image, and scripts loaded without defer .

Which fixes need a developer

Finding

You can do it

Needs a developer

Apps nobody uses

Uninstall them

Remove the code they left in the theme

A slow app embed

Switch it off, or choose a lighter app

Replace the app with theme code

Unused tags

Remove them in the tag manager

Change how the remaining tracking loads

Too many sections, oversized images, heavy video

Yes

Main image lazy-loaded or animated in

Scripts that block rendering

Slow Liquid

Layout shifting as widgets and fonts load

Theme several versions behind

Update, if the code has never been edited

Merge the edits into the new version, or rebuild

The developer work in the right-hand column is what Shopify speed optimisation covers. To stop the store drifting back, the monthly checks are part of maintenance and support .

When to stop tuning

Two cases where more tuning is the wrong answer.

If the theme is old and has been edited by several people, each fix uncovers another. Rebuilding on a current theme, with only the apps you still need, can cost less than repairing it. See custom Shopify theme development .

If the real-visitor numbers are already good and sales are still weak, speed is not the problem. Look at the funnel instead, starting with conversion optimisation for Shopify stores .

Frequently asked questions

What is a good speed score for a Shopify store?

On Google's Lighthouse scale, 90 or above is good, 50 to 89 needs improvement and below 50 is poor. For a sense of scale, Shopify requires Theme Store themes to average at least 60 across the home, product and collection pages. The score is a lab test, though. The numbers that describe your visitors are the Core Web Vitals in Shopify's web performance report.

Do apps slow down a Shopify store?

They can. Shopify names installed apps as one of the three things that affect a store's performance, along with the theme and third-party code you have added. Some apps also add code to the theme that is not removed when the app is uninstalled, so a store can be slowed by apps it no longer uses.

Will better hosting or a CDN make my Shopify store faster?

No. Shopify hosts every store on its own infrastructure with a CDN run by Cloudflare, and you cannot move a Shopify store to other hosting. The gains are in what the pages load, not where they are served from.

Can a slow store be fixed without changing the theme?

Often, yes, if the theme is current and the weight comes from apps, scripts, images and sections. When the theme itself is old or has been edited many times, rebuilding on a current theme can cost less than tuning it. A developer should tell you which case you are in before quoting.

Sources

Shopify Help Center: web performance reports · read 2 October 2026

Shopify Help Center: improving your online store performance · read 2 October 2026

Google: about PageSpeed Insights · read 2 October 2026

Shopify developer docs: performance best practices for themes · read 2 October 2026

Shopify developer docs: Shopify Theme Inspector for Chrome · read 2 October 2026

Shopify Help Center: app blocks and app embeds · read 2 October 2026

Shopify Help Center: uninstalling apps · read 2 October 2026

Shopify Help Center: duplicating themes · read 2 October 2026

Shopify Help Center: updating themes · read 2 October 2026

Related

Shopify speed optimisation

Shopify store maintenance and support

Core Web Vitals optimisation

Why is my website slow? How to fix it

Custom Shopify theme development

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