Case Study: deNatura.cz & Shoptet - Green Core Web Vitals and a 17% increase in Google traffic

Through successful multilateral collaboration, we at PageSpeed.cz improved our client's e-shop speed, resulting in increased traffic from Google.

Significant improvements in Core Web Vitals metrics led to a 17% increase in traffic from Google searches for deNatura.cz.

Join us as we explore the story behind this successful speed optimization.

Optimization of deNatura.cz

The client from deNatura.cz approached us with issues related to unwanted layout shifts (CLS), which were later compounded by slow interaction response times (INP).

Google evaluates websites for SEO and PPC based on the worst color of certain speed metrics. At that time, deNatura.cz received a red rating on mobile, which negatively impacted its starting position.

The website runs on the Shoptet platform, which we know performs well in terms of speed by default. Therefore, we at PageSpeed.cz began investigating the root causes of the issues.

Developers often adjust the website's appearance using JavaScript during design changes, causing unpleasant layout shifts.

What did we adjust at this stage? Here are a few examples of optimizations from two SpeedSprint analyses we prepared for the client:

1. We fixed appearance changes made with JavaScript.
2. We consistently reserved space for images to prevent layout shifts.
3. We modified the carousel appearance on the homepage before initializing JavaScript.
4. We began to work more efficiently with the code that caused freezing.
5. We optimized the number of operations triggered simultaneously by JavaScript.

Gradually, thanks to our experience optimizing other Shoptet-based websites, we concluded that to improve the interaction response time metric (INP), we needed to look beyond the platform itself.

Optimization of the Shoptet platform

At PageSpeed.cz, our mission is to enhance websites through speed optimization. This is best achieved through impactful collaboration.

Shoptet operates over 40,000 e-shops, and we are pleased to have assisted the development team of this largest Czech e-commerce platform in optimizing interaction response times.

What did we work on in this case? For instance, optimizing long tasks in JS generated by the cookie banner or finding better solutions for lazy loading images.

The result was green Core Web Vitals metrics not only for deNatura.cz but also for thousands of other websites on Shoptet. This also provided a bonus in the form of better ratings in SEO and PPC on Google.

Improvement in interaction response times (INP metric) following the joint optimization by PageSpeed.cz and Shoptet.

We thank the Shoptet team for their excellent collaboration, and we are glad they feel the same way:

We highly recommend collaborating with PageSpeed.cz. We appreciate their expert approach, quick communication, and concrete suggestions that had a real impact on improving the performance of thousands of our e-shops. The optimization went smoothly, and the results speak for themselves.

Denis Chripák, Engineering Team Lead at Shoptet

Optimization results: green Core Web Vitals and a 17.3% increase in traffic from Google

After all optimizations, deNatura is now performing very well in terms of website speed.

State of metrics before and after optimization.

Core Web Vitals metrics are green and significantly improved. This could also impact the website's business, right?

Thanks to the work of deNatura.cz's analyst, Milana Merglevského, we now see the impact in data from Google Search Console:

1. The first visible positive results came from optimizing Core Web Vitals metrics on deNatura's website (see point 1 in the image below).
2. Optimizing INP on the Shoptet side and achieving green Core Web Vitals on deNatura's website (point 2 in the image below) significantly contributed to improving average positions and thus clicks and impressions in Google search results.
3. In the period following implementation (November–December 2024), there was a total increase in sessions of +17.3% compared to the modeled scenario.

Image from Milana Merglevského's analysis showing the impact of changes on website traffic from organic Google searches.

Methodology notes:

• Data from Google Search Console are cleaned of brand search queries to eliminate the effect of brand campaigns.
• The effect of the second change is statistically significant (p < 0.001).
• The model in the analysis uses historical data from January to October 2024 as a training sample and accounted for the influences of other marketing channels and Czech public holidays.

We thank everyone involved in this complex yet highly successful collaboration, both from deNatura and the Shoptet platform.

Experts from PageSpeed.cz continually surprise me with how they push their outputs and capabilities. The current collaboration with deNatura.cz is once again fantastic, and I'm not exaggerating. The team found solutions to issues that were previously unsolvable. As a result, we have an e-shop full of important visual content that operates at super speed. Thank you very much!

Jan Kvasnička, co-owner of deNatura.cz, UX designer, and CRO specialist