When optimizing the website of a fashion eCommerce client in a highly competitive market, one key factor to stand out is site speed. In today’s digital world, a fast-loading website can make all the difference in retaining customers and improving conversions.
One of the best (and free) tools to assess your website’s performance is Google PageSpeed Insights. It analyzes your site and highlights areas for improvement, providing recommended solutions based on real user data. Powered by the Chrome User Experience Report (CrUX) dataset, it offers valuable insights into how users experience your site’s speed. You can explore more about it here.
When optimizing an eCommerce website for speed, there are several common issues that often arise, impacting both user experience and performance metrics:
- FCP (First Contentful Paint) Issue: The website's first screen loads slowly, delaying the first meaningful visual response to the user.
- LCP (Largest Contentful Paint) Issue: Too many image resources are loaded on the first screen, preventing critical content from rendering quickly. This causes delays in loading essential elements.
- CLS (Cumulative Layout Shift) Issue: Asynchronous loading of certain components causes elements on the page to shift, leading to a jittery and unpredictable user experience.
- INP (Interaction to Next Paint) Issue: Too many embedded time triggers or scripts run too frequently, making user interactions appear stuck or delayed, which diminishes the overall responsiveness of the site.
To address the identified performance issues, the team implemented a comprehensive solution that combined real-time data collection with front-end and back-end optimizations.
Sentry Installation
The first step was to identify where the performance problems were occurring. Since Google PageSpeed Insights updates data weekly, it wasn't providing real-time insights. To bridge this gap, we installed Sentry to collect real-time data and pinpoint exactly where the issues were arising. This allowed us to take immediate action.
Browser Plugin Installation: Core Web Vitals Visualizer
We also installed the Core Web Vitals Visualizer browser plugin. This tool allows us to see performance issues directly in the browser, helping us quickly locate specific problem areas on the website. After addressing the issues, we used Sentry again to monitor the improvements and track real-time performance.
- Switching to Server-Side Rendering: On mobile, the website was originally relying on client-side rendering, which depends on the loading status of the user’s device. We moved to server-side rendering, which pre-renders content on the server, making the page load faster.
- Asynchronous Loading of Resources: We optimized the front-end resource loading by asynchronously loading image resources that are not in the visible area (e.g., footer payment sprites). This ensures that only the visible content is prioritized for loading.
- Reserved Placement for Space-Hogging Modules: For modules that require significant space (e.g., ads, banners), we pre-allocated space to prevent shifts in the layout, reducing Cumulative Layout Shift (CLS).
- Merging Rendering-Related Interfaces: We merged interfaces related to page rendering to avoid layout shifts when components are opened, thus improving both Largest Contentful Paint (LCP) and CLS metrics.
- Optimizing DOM Output Size: We streamlined the size of the DOM output to reduce unnecessary elements and improve loading times.
- Optimizing Interface Return Data: By ensuring that only necessary data is returned from the backend (removing redundant fields), we reduced the payload size, speeding up page load times.
- Nginx Cache Optimization & Full-Page Caching: We implemented Nginx cache optimization and used Redis to support full-page caching for specific languages and regions (e.g., US-EN-USD), which further accelerated website loading by caching dynamic content.
The data after optimization clearly demonstrates that improving website performance not only boosts user satisfaction but also drives sales growth and strengthens brand competitiveness.
Enhancing the user experience directly contributed to a higher conversion rate. Faster page loads, more stable layouts, and smoother interactions all ensured a seamless experience, especially during key actions like purchases or registrations. This resulted in more successful conversions, as users could navigate the website efficiently without frustration.
A faster, more efficient website helped establish stronger brand trust. With a smoother, more reliable user experience, visitors were more likely to return, fostering brand loyalty and encouraging positive word-of-mouth. The improved site performance made users feel more comfortable engaging with the brand, leading to a higher revisit rate.
By monitoring key performance indicators (KPIs) before and after the optimization—such as reducing FCP by 1 second, maintaining CLS within 0.1, and significantly improving INP—we gained actionable data to support future marketing and product decisions. These metrics not only guided internal improvements but also provided solid proof of the optimization’s success.
Optimizing Core Web Vitals (FCP, CLS, and INP) brings significant SEO benefits. Search engines like Google use these performance indicators as contributing factors to page experience evaluations. When these metrics meet Google’s recommended standards, websites tend to rank higher, improving visibility in search results.
With a higher website ranking, the business saw an increase in organic traffic. This meant more users could discover the site via search engines, leading to greater opportunities for conversions. The improved performance attracted potential customers and led to higher engagement and sales.