The Fastest E-Shop of 2024: Common Mistakes, What Works, and What Sets the Winner Apart?

In our previous blog post, we announced the fastest e-shop of 2024. It is iWant.cz, and we heartily congratulate its creators, as well as the teams behind Hornbach.cz and Altisport.cz, who also made it to the podium.

But what do the data reveal, and what can you learn from them, beyond comparisons with the largest (and fastest) Czech e-shops? In this text, we focus on common errors that e-shops repeatedly make, optimization recommendations that always work, and finally, we take a closer look at the contest winner.

Common E-Shop Mistakes When It Comes to Speed#

When we examine the less successful e-shops on our list, we find very similar errors to those we encounter with many of our clients at the start of web speed collaboration.

1. Poorly implemented lazy loading on images. Lazy loading is either missing entirely or mistakenly applied to everything, including the main element for the LCP metric. Generally, developers often mismanage loading priorities.
2. Ignoring image dimensions, worsening the CLS metric. Yet it's so simple: just add width and height attributes to <img> elements.
3. Skipping fundamental optimizations like reducing data size for images, web fonts, CSS, or JS files.
4. Forgetting that server response is the foundation of everything. Websites at the bottom of the ranking have a TTFB metric that is significantly worse on average than the fastest ones. For example, bauhaus.cz shows a 75th percentile server response time on mobile of 1.84 seconds, while competitor Hornbach.cz manages it three times faster—at 0.58 seconds.
5. Poorly optimized analytics and an excess of third-party scripts. With the advent of the INP metric, we can measure interaction delays caused by analytics. All the fastest e-shops keep mobile INP below the recommended 0.2 seconds, but for instance, Bibloo.cz's 75th percentile for this metric is five times that, over one second.

In our efforts to popularize web speed, we always say that speed optimization is not a checklist to be completed nor "a bit of magic" (like SEO, perhaps). Speed optimization is an exact discipline, where we identify a problem and find the most efficient solution possible.

Scanning the fastest e-shops, and also from our own experiences at PageSpeed.ONE, show that there are certainties you can always rely on, and they'll serve you well.

What Almost Always Works for E-Shop Speed Optimization?#

1. LCP Metric: Use WebP format for images everywhere; they are almost always more data-efficient than JPG and even replace PNG. The brave might opt for AVIF format.
2. LCP Metric: loading=lazy, meaning lazy load images, on all <img> elements outside the first screen.
3. LCP Metric: Use <link preload> to preload web fonts used in the first user viewport.
4. CLS Metric: Always add width and height attributes to all content images, i.e., <img> elements.
5. CLS Metric: Implement the size-adjust descriptor in typography to match the size of system fonts with web fonts.
6. INP Metric: Respond immediately in the interface, giving users instant feedback.
7. Consider optimizing for fast navigation types like Speculation Rules and back/forward cache.
8. Speed always degrades over time. Therefore, speed monitoring is fundamental.

Dissecting the Winner iWant.cz#

What is handled inspiringly on iWant.cz from the perspective of web speed optimization?

Let's take a few tips:

1. Servers here are blazing fast. The TTFB metric value on mobile for the entire iWant.cz domain is 0.37 seconds, a phenomenal result at half the value recommended by Google. Faster still is Zalando.com (0.24 seconds), a figure that truly leaves us in awe given the scale of such an international project.
2. Good work with loading priorities. We see finely tuned lazy loading for less important images (loading=lazy) and acceleration of critical elements using <link preload>.
3. Optimized images in WebP format. Given the type of website and showcased products, reducing data size by lowering quality is hardly possible. Further optimization room is offered only by transitioning to the AVIF format.
4. Very economical handling of CSS and JavaScript. Custom styles on the critical product detail page type are just about 15 kB (!), with JavaScript files slightly over 100 kB. In an era of downloading megabyte files that users don't need at the moment, this is quite a phenomenon.

We are delighted to have had the honor of assisting the Smarty.cz team with speed optimizations. However, it must be said that recently, our involvement has only involved minor corrections. The web team here is already very knowledgeable and can independently continue to improve speed.

That concludes this year's study of the fastest Czech e-shops. We look forward to the results of future years and wish you, as web developers and users, fast websites!

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Need help with your e-shop's speed or monitoring? Get in touch.

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