Why is my Shopify store slow? How to find the cause and fix it

A slow store rarely becomes slow in one day. An app here, a tracking code there, a bigger main image for the campaign, and after a year the product page takes noticeably longer to appear on a phone than it did at launch. A slow store costs sales: some customers leave before the page has even opened.

The good news is that you do not have to guess. Shopify measures your store’s speed from real customers, and the causes are almost always the same handful of things. This is how we find and fix them.

Start with what Shopify has measured

Your Shopify admin already has the numbers. The Online Store page (your theme library) shows a summary of the past 30 days, and the full reports are under Analytics > Reports: search for contentful, next or cumulative.

You need the Reports permission to see them. While your store is still behind a password, no real visitor data is collected, so the numbers start once the store is open.

Shopify tracks three numbers, the same ones Google uses to judge how pages feel to use:

What Shopify measures	Name in the report	Good	Poor
How fast the most important content, usually the main or product image, appears	Largest Contentful Paint (LCP)	2.5 seconds or less	over 4 seconds
How quickly the page reacts when a customer taps or clicks	Interaction to Next Paint (INP)	0.2 seconds or less	over 0.5 seconds
How much the content jumps around while loading	Cumulative Layout Shift (CLS)	0.1 or less	0.25 or more

A result is good when three out of four customers get at least that fast an experience. The reports also mark app installs and theme changes on the timeline, which often shows exactly when the store got slower. In between is a moderate level: not alarming yet, but worth improving.

Find the slow page

The overall number tells you whether there is a problem, not where it is. Two reports, found with the same search, show that:

• Page type splits the numbers by kind of page: home page, product page, collection, cart and so on. If only product pages are red, start there.
• Page URL lists single pages. That is where you find, say, a campaign page whose large image slows the whole page down.

The numbers can lag by up to a day and a half. After a fix, give it at least two weeks before you judge the result.

To see what slows down a single page, Google’s free PageSpeed Insights tool lists the causes. Its score is only a test on one imagined phone, though. Your real customers’ experience is in the Shopify reports.

What usually slows a store down

1. Apps you no longer need

Every app that adds something visible to your store loads its own code, often on every page. Shopify itself recommends removing apps you do not use and apps that do the same job as another one.

• Go through your apps and remove the ones you no longer use.
• In the theme editor, open App embeds and switch off the ones you do not need.
• Older apps could add code straight into the theme, and it can stay behind after the app is removed. If your store is a few years old, ask a developer to check the theme for leftovers from removed apps.

Example: Vorssa Ink’s theme still carried code from apps that were no longer in use. After the clean-up, the home page went from 11.4 MB to 3.5 MB, and layout shift while loading (CLS) fell from 0.15 to 0.01. Read the full Vorssa Ink theme redesign.

2. The main image loads too late or is too large

The large image at the top of the page is usually what the customer is waiting for. The most common mistake is that the theme tells the browser to load it later, the same way as images further down the page.

• The first image in view loads straight away, and images further down load when the customer scrolls to them.
• Phones get a small image and large screens a large one. Shopify does this for you when the theme uses its built-in image tools.
• Do not fade the main image in with an animation. It looks nice, but the customer waits longer to see it.

For your developer: no loading="lazy" on the first image, fetchpriority="high" instead, and images through the image_url and image_tag filters with widths and sizes.

3. Chat, reviews and tracking codes

Chat windows, review widgets, testing tools and tracking codes compete with your store’s own content. Most of them can wait until the page is open.

• Remove tracking codes whose data nobody looks at.
• Let the chat load only when a customer opens it.
• Switch off testing tools when no test is running.

For your developer: load non-essential scripts with defer or async.

4. Too many fonts

Every font and every weight is its own file that has to load before the text looks right. One or two fonts and only the weights you really use are enough for most stores.

5. Content that jumps

A banner or image that appears late pushes everything down just as the customer is about to tap, and they hit the wrong thing. Space for images should be reserved in advance, and the same goes for announcement bars and app widgets.

6. Large catalogues and a heavy theme

If collection pages are slow only with a large catalogue, the cause may be in the theme code. A theme that is fast with ten products can be slow with a thousand. Fixing that is a job for a developer.

Make the changes safely

Speed fixes change the theme of a live store, so we never make them in the published theme. We make each change on an unpublished copy of the theme first, test it, check it on a phone and only then publish it. We explain the workflow in Stop editing your live Shopify theme.

After publishing, follow the Shopify report for a couple of weeks. That shows whether the change really helped your customers.

When to ask for help

If your numbers are in the red and the cause is not obvious, the problem is often an app that cannot be removed, a heavily customised theme or code added years ago that nobody remembers. That is where an experienced Shopify developer saves you time: we measure, fix the biggest causes first and show the before and after in your own Shopify reports.

Sources: Shopify’s web performance reports in the Help Center and the performance best practices for themes on shopify.dev.

Want to know what slows your store down? Ask Virta below.