Shopify stores slow down for predictable reasons. Too many apps running JavaScript on every page, images that were never optimised before upload, themes with bloated code and third-party scripts loading before the page content. Most speed problems are fixable without rebuilding the store. The starting point is knowing where the time is actually being lost.
Why speed matters for Shopify revenue
The relationship between page load time and conversion is well established. A one-second delay reduces conversions by around 7%. Google also factors page speed into search rankings, particularly on mobile. For a Shopify store that depends on both organic search traffic and paid traffic, a slow site spends more to acquire buyers and then loses some of them before they complete a purchase. The cost compounds.
What slows Shopify stores down
The most common causes of slow Shopify stores, in rough order of frequency: apps that inject JavaScript on every page regardless of whether that page uses the app's functionality, unoptimised product images, themes that load full-page scripts for features only used on a few pages and too many third-party tracking scripts running simultaneously before the page content renders.
A store that has been adding apps over several years without removing unused ones will almost always have a speed problem. Each app that injects a script adds load time. Ten apps adding 200ms each is two extra seconds of loading before a buyer sees a product.
The app audit
Before making any other changes, audit the installed apps. For each app: is this still being used actively? Is the function it provides worth the speed cost? Can the same function be handled by a different app with a lighter footprint, or built into the theme directly? Apps that were installed to solve a problem that no longer exists should be removed. Apps that load scripts site-wide but only have functionality on specific pages should be configured to load selectively where the app allows it.
Images: still the most common culprit
Shopify handles some image optimisation automatically, but it cannot fix a source file that was uploaded at full camera resolution. Product images should be resized to the largest size they will be displayed before upload, saved in a web-appropriate format and compressed without visible quality loss. Tools like Squoosh or TinyPNG handle this without specialist knowledge. The improvement from getting images right is often the single largest speed gain available on a poorly optimised store.
What a speed audit finds
A proper Shopify speed audit uses tools like Google PageSpeed Insights and WebPageTest to identify exactly where time is being spent in the page load sequence. The output will show which scripts are blocking render, which images are oversized and what the actual load time is for a visitor in New Zealand. That last point matters. A store built and tested on a US connection may feel fast to the developer and slow to the NZ buyer it is actually serving.
Theme code and render-blocking resources
A slow theme is a structural problem, not a configuration one. Themes that load large JavaScript files before the page content renders will be slow regardless of how well images are compressed or how many apps have been removed. The technical problem is render-blocking: scripts that sit in the loading sequence before the browser can display anything to a visitor. The symptom is a page that feels like it loads all at once after a delay, and a high Time to First Byte on speed testing tools.
For most businesses, switching to a faster theme is more practical than rewriting theme code. The Shopify theme store includes speed ratings for listed themes, and the difference between a well-optimised theme and a poorly-optimised one can be a second or more of load time on mobile. If a speed audit identifies the theme as the primary constraint, the question becomes whether the retheme cost is justified against the conversion gain. In most cases for NZ stores with meaningful traffic, it is.
Redirect chains
Every 301 redirect adds a small delay as the browser follows the chain from the original URL to the destination. A single redirect is inconsequential. A chain of three or four redirects, accumulated through product renames, collection restructuring or a previous migration, adds measurable load time, particularly on mobile connections. Shopify stores that have migrated from other platforms or undergone significant URL restructuring commonly have redirect chains buried in their setup, visible only through a crawl tool.
Cleaning up redirect chains is straightforward but requires auditing all active redirects and identifying where chains exist. Collapsing a three-step chain into a direct redirect eliminates the intermediate load steps and can also improve how search engines process the redirected pages.
Prioritising the fixes
Not all speed improvements produce equal results. An hour spent removing unused apps will typically produce a larger measurable improvement than an hour spent optimising JavaScript loading order. Images not optimised before upload are often the largest single gain available on stores that have never addressed the issue. A proper audit identifies the specific bottlenecks in your store and prioritises fixes by impact, so development time and operational changes go to the things that actually move the score rather than the things that are technically interesting.
The target for a well-optimised Shopify store serving NZ customers is a Google PageSpeed score above 70 on mobile and a Largest Contentful Paint under two and a half seconds. Both are achievable without a rebuild for most stores where performance has been neglected rather than architecturally broken. A store scoring 30 due to app bloat and unoptimised images can realistically reach 65 to 70 through operational changes alone. Getting from 70 to 90 typically requires theme-level work and is a developer engagement rather than a configuration task.
Frequently asked questions
What is a good Shopify speed score?
Shopify's built-in speed score runs from 0 to 100. A score above 50 is considered average. Above 70 is good. The Shopify speed score is one indicator, but Google PageSpeed Insights gives a more detailed breakdown of what is actually causing delays and is more directly tied to how Google measures site performance.
How do I check my Shopify store's speed?
In Shopify Admin, go to Online Store then Themes. Your speed score appears on the theme dashboard. For more detail, run the store URL through Google PageSpeed Insights at pagespeed.web.dev and WebPageTest at webpagetest.org. Both are free and give actionable diagnostics.
Do Shopify apps affect site speed?
Yes, often significantly. Apps that inject JavaScript on page load add to the time before the page is interactive. This is the most common cause of Shopify speed degradation over time, as stores accumulate apps without removing the ones no longer in use. Auditing and removing unnecessary apps is typically the fastest speed improvement available.
