This article explains in simple terms how our team of professional Shopify website developers approach improving the speed of a Shopify website.
Speed is one of those topics that everyone agrees is important right up until the realities of the recommendations from a PageSpeed Insights report sink in. This is often followed by platform-based excuses: “Shopify is just slow.” “It’s the apps.” “It’s Google being fussy.” In reality, plenty of Shopify stores are fast. They feel snappy on mobile, they load product pages without lag, and they stay stable even with a rich feature set. The difference is rarely the platform. It’s the build.
Google’s Core Web Vitals are not the only way to measure performance, but they are a good shorthand for whether the site feels quick and reliable to real users. They also overlap with commercial outcomes: when pages load faster and interactions feel smoother, conversion rates tend to improve. If you’re serious about eCommerce, speed has to be a consideration, so let’s dive into how we improve it. If you need any more information on Shopify, make sure to head over to our Ultimate Guide to Shopify Website Development.
First: what Core Web Vitals actually mean on a Shopify store
Core Web Vitals change over time, but the underlying idea is consistent. Google is measuring whether a page loads quickly, whether it stays visually stable while loading, and whether it responds promptly when a user interacts with it.
On Shopify, those user experiences are largely shaped by the theme and by third-party scripts, meaning Shopify’s core infrastructure is rarely the bottleneck. The most common issues come from a theme that ships too much JavaScript, a page that loads too many heavy assets upfront, or a site weighed down by app scripts firing on every template.
A performance-focused approach starts by accepting a basic truth: you can’t optimise what you don’t control. That’s why good speed work begins with solid architecture decisions, not micro-tweaks.
We treat performance as a build requirement, not a post-launch clean-up
One reason performance projects fail is that they are left until the end. The theme is built, the design is approved, the app stack is installed, and then someone asks why pages are slow. At that point, improvements often feel like compromises as you’re forced to remove features, simplify interactions, or accept a less refined experience for your users.
The better approach is to bake performance into the definition of “done”. That means performance constraints influence everything from design to component choice to how scripts are loaded. It also means performance is measured throughout development, not guessed.
A practical example is imagery. If a design relies on huge uncompressed images, no amount of JavaScript minification will fix the experience. Similarly, if the theme is built with heavy libraries for minor UI effects, the problem is structural, not cosmetic.
Our approach begins with the “performance budget” mindset
A helpful way to think about speed is to treat the site like a budget you are spending. Every script, font, animation, tracking tag, and marketing tool has a cost. If you spend the whole budget on widgets before you’ve even loaded the product content, the user experience suffers.
In a Shopify build, we typically establish a performance budget early. It doesn’t have to be overly formal, but it does need to influence decisions in a real way. For example, we might decide that product pages must remain lightweight enough to load quickly on mid-range mobile devices, or that the theme will avoid certain libraries unless they genuinely justify their weight.
This changes conversations. Instead of “can we add this?”, the question becomes “what’s the cost, and what do we remove or adjust to pay for it?”
The biggest Shopify speed win: controlling JavaScript
Most performance problems on Shopify stores can be traced back to JavaScript. Not because JavaScript is inherently bad, but because it is easy to overuse. The web has drifted toward increasingly script-heavy experiences, even when the functionality could be delivered with simpler patterns.
A fast Shopify theme tends to do a few things consistently. It keeps interactive code minimal and purposeful. It avoids loading scripts globally when they are only needed on certain templates. It reduces reliance on third-party dependencies. And it accepts that not every interaction needs to be unique.
This is especially important on mobile. Heavy JavaScript can increase the delay between a user tapping a button and the site responding. That delay is a killer for conversion. Users don’t interpret it as “JavaScript execution time”. They interpret it as “this site feels clunky”, and depending on the button affected, it can even lead to usability issues with key site features like the basket or checkout.
Load what’s needed, when it’s needed
A simple but powerful principle is conditional loading. Product pages need certain scripts. Collection pages need others. Some features are only required for particular templates or particular customer journeys. Loading everything on every page is one of the more common reasons Shopify stores become slow over time.
Well-built themes load scripts conditionally, and where possible they defer non-critical scripts until after the main content is visible. We also pay close attention to third-party tools. It is common for marketing tools to inject scripts on all pages, whether they are needed or not. When you add five of these tools, you often end up with a store that is effectively competing against itself for load time.
This is where a specialist Shopify team adds value: they understand the trade-offs and know where script bloat tends to hide.
Images, fonts, and layout stability: the “quiet” causes of sluggishness
Performance work is often framed as a coding exercise, but many of the most impactful improvements are about asset handling and layout stability.
Images are a huge factor in ecommerce. They are also one of the easiest ways to sabotage speed. A fast Shopify theme uses responsive images correctly, requests appropriate sizes, and avoids loading heavyweight assets above the fold unnecessarily. Shopify provides a powerful image system, but the theme still needs to implement it properly. If the theme is careless, it will request larger images than necessary or cause visible layout shifts as images load.
Fonts are similar. It is surprisingly common for sites to load multiple font families and weights, even when the design only uses a small fraction. Each font file has a cost, particularly on slower connections. A performance-driven approach is to be disciplined: load what you need, and don’t treat typography as weightless.
Layout stability matters too. When elements move around as the page loads, the site feels broken, even if the customer cannot articulate why. Good themes reserve space for images, avoid injecting late-loading content above the fold, and keep page structure predictable and stable throughout the load process.
Managing apps without falling into performance debt
App stacks are where Shopify performance often lives or dies. A single well-built app is usually fine. Ten apps that all inject scripts and styles can seriously damage the experience.
The key is not “never use apps”. The key is to treat apps as part of the performance profile. We typically audit the app stack in three ways. First, we look for features that overlap, because duplicated functionality usually means duplicated scripts. Second, we look at which apps inject sitewide code and whether that injection can be limited to relevant templates. Third, we look at whether a feature is better handled through theme-native code in order to reduce weight.
This is also where merchant teams can inadvertently create performance issues over time. A store adds a pop-up tool for one campaign, a new review widget, a gifting app, a new analytics tag, and so on. Each addition is reasonable in isolation. Collectively, they can turn a fast store into a sluggish one.
That’s why speed is more than a one-off project. It’s an essential regular checkup for every website, and each appointment needs to be approached with the mindset that it might need more work.
How we test: looking at the site as customers actually experience it
Performance testing should reflect real-world users, not ideal lab conditions. That means testing on mobile, on mid-range devices, and on average network speeds. It also means using more than one tool, because no single metric tells the full story.
In practice, we combine lab tools with field insights. Lab tools can show you what assets are heavy and what scripts are blocking. Field data, when available, tells you how real users experience the store over time. We also test the pages that matter most commercially: home page, key collection pages, top-selling product pages, cart flows, and any landing pages used for paid campaigns.
The goal is simple: pages should feel fast and stable. You want customers to reach product information quickly, scroll smoothly, and interact without delay.
A realistic view: “perfect scores” are not the aim
One of the biggest traps with Core Web Vitals is chasing scores for their own sake. In eCommerce, you are balancing performance with functionality. There are times where a feature is worth a small performance cost because it improves conversion or operational efficiency. The key is knowing the cost and making the choice deliberately.
A specialist Shopify team aims for strong real-user experience, not scores that have no real-world benefit. If the store loads quickly, feels responsive, and remains stable under real conditions, you’ve achieved what you need to. That is what customers reward, and it is what Google tends to favour.
Conclusion
Core Web Vitals have simply made something visible that has always been true: fast stores convert better. On Shopify, speed is mainly a function of theme architecture, asset discipline, and how the app stack is managed. The best results come when performance is treated as a build requirement from day one, and when the store is maintained with the same discipline after launch.
If you are unsure whether your store is genuinely fast – not just “fast on Wi-Fi”, but fast in real customer conditions – a performance audit is often the quickest way to identify where the time is being lost. The fixes are frequently more straightforward than merchants expect, but only if you approach them systematically.
We can conduct that audit for you, and make sensible recommendations that will progress your business goals. Get in touch today.
