In short: Most slow Shopify stores are slowed down by what has been added on top of Shopify: too many apps, tracking scripts, oversized images, an old theme, fonts, late-loading pop-ups and heavy collection pages. Measure with field data first, then start by removing the apps and scripts you no longer use.
A slow Shopify store costs you orders, and it costs you more on mobile, where most of your traffic is.
The good news: Shopify’s infrastructure is fast. When a store is slow, it is almost always something added on top of it.
Below are the causes we find most often when we audit slow stores, roughly in the order we find them, and what to do about each.
First, measure the right thing
Most people start with a Lighthouse score. That is a lab test, run once, on a simulated device. Useful for debugging, but it is not what your customers experience.
What matters is field data: how real visitors experienced your store over the last 28 days. You can find it in two places:
- Shopify’s web performance reports (Analytics > Reports in your admin)
- PageSpeed Insights, in the “Discover what your real users are experiencing” section at the top
Google’s Core Web Vitals give you three targets, measured at the 75th percentile of visits:
- Largest Contentful Paint (LCP): 2.5 seconds or less. How fast the main content shows up.
- Interaction to Next Paint (INP): 200 milliseconds or less. How fast the page responds when someone taps or clicks.
- Cumulative Layout Shift (CLS): 0.1 or less. How much the page jumps around while it loads.
Check mobile first. That is where stores fail.
1. Too many apps
This is the number one cause we see.
Many apps add their own scripts and styles to every page of your store, whether that page uses the app or not. Ten apps can mean ten extra things to download before your store is usable.
Uninstalling is not always enough either. Older apps often leave code behind in your theme files after you remove them.
The fix: list every installed app and ask whether it still earns its place. Remove the ones that do not, then check your theme code for leftovers from apps you have already removed. For simple features like badges, size charts or announcement bars, build them into the theme instead.
2. Tracking and marketing scripts
Pixels, chat widgets, review widgets, heatmaps, affiliate tags. Each one is small. Together they are often the heaviest thing on the page, and they are the main reason stores fail INP.
We regularly find the same pixel installed twice, or tools from a vendor the brand stopped using a year ago.
The fix: audit every script in theme.liquid and remove duplicates and dead tools. Where your ad platforms support it, run tracking through Shopify’s customer events and pixels instead of pasting scripts into the theme.
3. Oversized images and hero media
A 4,000 pixel hero image squeezed into a phone screen. An autoplaying background video. A homepage carousel with eight full-width slides.
This is usually the main reason for a slow LCP.
The fix: serve images at the size they are displayed. Shopify’s image_url and image_tag Liquid filters generate responsive sizes for you. Never lazy-load the main image at the top of the page, but do lazy-load everything below the fold. And question every autoplay video and carousel on mobile.
4. An old or heavily patched theme
A theme that has been patched for five years by three different agencies carries all of that history. Old Online Store 1.0 themes in particular were built before Shopify’s modern theme architecture.
The fix: sometimes the cheapest speed project is a new foundation. When we moved Nc’nean from a 1.0 theme to Shopify’s Horizon theme, Largest Contentful Paint dropped 18%, and the team could edit pages without a developer again.
5. Too many fonts
Every font weight is a separate file. Two typefaces in four weights each is eight downloads before your text looks right.
The fix: stick to two or three weights, and use fonts from Shopify’s font library where you can.
6. Layout shifts from late-loading elements
Pop-ups, promo bars and review stars that appear after the page has loaded push everything else down. Customers tap the wrong thing, and your CLS fails.
The fix: reserve space for anything that loads late, and make sure every image has a width and height set.
7. Heavy collection and search pages
Collection pages with 50 or more products, swatches loading every variant image, and filter apps adding their own scripts on top.
The fix: show fewer products per page, load swatch images only when needed, and use Shopify’s native filtering where it covers your needs.
What not to do
Be careful with “speed booster” apps that promise a perfect score. Installing another app to fix too many apps rarely ends well, and some of them delay scripts in ways that quietly break your tracking.
A fast store is usually a store with less on it, not one with another layer on top.
Where to start
If you only do one thing this week: remove the apps and scripts you no longer use. It is free, low risk, and it is where most of the gains are.
If you want to see where your store stands first, run our free store audit. If you want us to do the work, that is what our Shopify optimization service is for.
Frequently asked questions
What is a good speed for a Shopify store?
Why is my Lighthouse score low when my store feels fast?
Do Shopify apps slow down my store?
Will switching to the Horizon theme make my store faster?
Can I speed up my store without a developer?
Sources
- Web Vitals (web.dev)
- Web performance reports (Shopify Help Center)
- PageSpeed Insights
- Performance best practices for Shopify themes (Shopify.dev)
- Liquid filters: image_url (Shopify.dev)
- Pixels and customer events (Shopify Help Center)
Spotted something wrong or out of date? Email hello@kirkbyconsulting.com with the details and we will correct it.