Shopify store speed optimisation
The Shopify app ecosystem is built around a simple premise: there is an app for everything, and you should pay for it monthly. Review apps, loyalty apps, upsell apps, subscription apps, wishlist apps, size guide apps. Each one solving a real problem, each one adding its own JavaScript, its own CSS, its own server requests to every page your customers load.
At some point, most Shopify stores hit a wall. The store is slow. Google’s performance score is low. Mobile load times are painful. And the standard remove apps advice is not an option, because the business actually needs them.
This post is about what you can do instead. The practical steps I take when working on Shopify store speed optimisation without touching the tools your operations depend on.
Why apps slow your store down
Every third-party app that adds frontend functionality does so by loading its own code into your store’s pages. That means JavaScript files, stylesheets, and often a series of network requests to the app’s own servers, fetching personalisation data, loading widgets, tracking events.
The problem is not any single app. One well-built app with a small script has a negligible impact. The problem is accumulation. A store with ten active frontend apps is loading ten separate sets of code, often with no coordination between them, and often on every single page, regardless of whether that page actually uses the app.
The second problem is code quality. App developers are building for a broad market, their code needs to work across thousands of different Shopify themes, on stores with different configurations, different other apps, different usage patterns. That breadth comes at a cost: the code is often larger than it needs to be, more defensive than necessary, and sometimes poorly optimised for production.
How to find what is actually causing the problem
Before fixing anything, you need to know what you are dealing with. The tools for this are free and already in your browser.
Start with your browser’s developer tools
Open your browser, right-click anywhere on your store, and select Inspect. The Network tab shows every file your page loads, JavaScript, CSS, images, fonts, and API requests. Sort by size. Sort by load time. Look for anything that stands out.
What you are looking for: large JavaScript files (anything over 100kb is worth investigating), requests that take more than 500ms, and files loading from third-party domains that are not yours or Shopify’s. Each of those domain names will correspond to an app.
Use Google PageSpeed Insights
Go to pagespeed.web.dev and enter your store URL. Run it on mobile, not desktop. Mobile is where Shopify stores typically perform worst, and it is what Google uses to determine your search ranking.
The report will flag specific issues: render-blocking resources, unused JavaScript, third-party code impact. These are your starting points, not your full diagnosis. The report tells you there is a problem; the Network tab tells you which app is causing it.
What store owners should understand
You do not need to implement any of this yourself. But having a surface-level understanding helps you brief clearly, evaluate what a developer is doing, and maintain awareness of your store’s performance over time, especially when working with employees or agencies who change.
- Know your current score. Run your store through PageSpeed Insights now, before any changes, and save the result. You cannot measure improvement without a baseline.
- Know which apps load on which pages. Ask your developer or agency to map this for you. If they cannot tell you, that is a problem.
- Treat performance as part of ongoing maintenance, not a one-time fix. Apps get updated. New features get added. A store that performs well today can degrade over six months without anyone noticing.
- Brief clearly. ‘The store is slow’ is not a brief. ‘Our mobile PageSpeed score is 34, the Network tab shows our review app loading 280kb of JavaScript on the homepage, and we want to understand whether it can be deferred or loaded only on product pages’, that is a brief.
The short version
- App accumulation is the primary cause of Shopify performance problems, not any single app, but the combined weight of many
- The browser’s Network tab and Google PageSpeed Insights are the right tools to diagnose the problem before attempting any fix
- As a store owner, your job is to know your baseline score, understand what is loading on your pages, and brief clearly