Why a Shopify store gets slow, and what to check first

Measure what your visitors actually get

Shopify reports speed from real visits. In the admin, the Themes page under Online Store shows a summary of three measures from the last 30 days of visits: how long the main content takes to appear (Largest Contentful Paint), how quickly the page responds to a tap (Interaction to Next Paint), and how much the layout jumps while loading (Cumulative Layout Shift). The web performance reports (opens in a new tab) under Analytics, then Reports, break each one down over time, by page and by page type.

Shopify counts these as good at 2.5 seconds or less, 200 milliseconds or less, and 0.1 or less respectively. A new store, or one still behind a password, may not have enough visits to show anything yet.

The over-time reports also mark app installs, theme updates and code changes on the chart, so a slowdown can often be traced to the week it started.

Lab tools such as PageSpeed Insights are useful for finding causes, because they list what loaded and in what order. A single lab score is not what your customers experience, though, and chasing one number can cost you features people use. For an outside view of a public storefront, the free Shopify store review lists the theme and the apps it can see and how heavy the home page is.

Apps, including the ones you removed

Many apps load their own code on every page, whether that page uses the app or not. Ten apps can mean ten extra files on the product page, each one competing with your photos for the connection.

Uninstalling an app does not always remove its code. Apps built with app blocks are removed from the theme automatically. App embeds, and code some apps wrote straight into theme files, can stay behind. Check the App embeds list in the theme editor, look for leftover snippets named after apps you no longer use, and ask the app's developer if you are unsure; Shopify's own guidance (opens in a new tab) is to check an app's removal steps before uninstalling.

Then look at what is still installed. Two apps doing the same job, an app bought for an experiment that ended, and apps loading on pages where they do nothing are the usual finds.

The image at the top of the page

On most store pages the largest thing on the first screen is a photo: the homepage banner or the main product image. That image is usually what the Largest Contentful Paint measure is waiting for.

Upload photos at a sensible size rather than straight from a camera, and let the theme ask for the width it needs; current Shopify themes do this for you, older or heavily edited ones sometimes load the original. Do not lazy-load the first image on the page, because lazy loading tells the browser to fetch it late.

A homepage slider with five large banners costs the download of five images for the one a visitor actually sees. One strong image usually does the same job.

Scripts you did not write

Chat widgets, review widgets, pop-ups, heatmaps and several analytics tags that measure the same thing each download and run on the visitor's phone. Individually they are small. Together they are often the main reason a page feels sluggish when someone taps a button.

Keep the ones you look at. Load the rest only on the pages that need them, or not at all.

Fonts and video

Every font family and every weight is another file. Two families in two or three weights is plenty for most stores.

An autoplaying background video on the homepage is one of the heaviest things a store can load on a phone. If it stays, give it a lightweight still image to show first.

Fix in the right order

Duplicate the live theme and make changes on the copy, one at a time, so you can tell which change helped and put anything back that broke. Preview the copy on a phone, not only on a desktop.

Remove before you add. A speed app that promises to fix everything adds its own script to the pile, and it cannot remove code another app left in your theme.

After publishing, give the 30-day summary time to move. It is a rolling window of real visits, so a fix shows up gradually rather than the next morning.

If you would rather hand the work over, the Shopify speed and conversion sprint covers it, on a copy of your theme.