How Rakuten 24 in investment in Core Web Vitals resulted in increase of 53.37% in revenue per visitor and an impressive 33.13% increase in conversion rate.


Rakuten 24 is a leading online store powered by Rakuten Group, Inc.—a global leader in internet services. It provides a wide selection of everyday essentials such as healthcare items, beverages, pet supplies, baby products, and more, collaborating with both major multinational and domestic consumer goods manufacturers. This store is one of the top performers on Rakuten's digital marketplace platform in Japan.

The Rakuten 24 team has been measuring, optimizing, and monitoring Core Web Vitals and other metrics in order to understand the impact of web performance on user experience. As a result, more than 75% of their users are enjoying good Largest Contentful Paint (LCP), First Input Delay (FID), and First Contentful Paint (FCP) scores. Nonetheless, they are still striving for improvements in Cumulative Layout Shift (CLS).

After analyzing the homepage data, the company found out that a good LCP Score can result in the following:

  • Increase of conversion rate upto 61.13%
  • 26.09% of Revenue per visitor
  • 11.26% of the Average Order Value
  • Good FID Score that increases conversion rate upto 55.88%

In order to further correlate Core Web Vitals and business metrics, Rakuten 24 also conducted an A/B test that was focused on optimizing the Core Web Vitals and other related metrics. Here's what they achieved.

  • 53.37% improvement in Revenue per visitor
  • 15.20% improvement in average order value
  • 33.13% improvement in conversion rate
  • 9.99% improvement in average time spent
  • 35.12% reduction in the exit rate.

Highlighting The Opportunity

Even though optimizing web performance is a smart investment to improve the user experience and business growth, Rakuten 24 team also understands how difficult it is to convince the stakeholders to adopt Core Web Vitals and focus on web performance. However, they believe that demonstrating the ROI of web performance optimization is the most effective way to gain approval.

Utilizing its flexibility as a new and independent service, Rakuten 24 took the challenge. They believe their case study will assist them in making more data-driven decisions in the future, as well as helping other developers gauge the impact of their work and demonstrate to their stakeholders that performance improvement is worth the investment.


Performance Measurement

To gain a more accurate understanding of user experience, Rakuten 24 determined to leverage the web-vitals JavaScript library to measure Core Web Vitals and other metrics in the field and transmit the data to their in-house analytics tool, in addition to using PageSpeed Insights for website auditing.

Performance Analyzing

The team examined the field data they gathered to see if there was any connection between Core Web Vitals and key business metrics. They discovered that those users who converted had a better LCP than those who didn't.

Performance Monitoring

The team constructed a dashboard for performance monitoring utilizing the data acquired in the field and a business intelligence tool. This is essential for tracking progress and avoiding any backsliding

A/B Test

The team conducted an A/B test to measure the business impact of their performance optimizations by optimizing one of their landing pages for Core Web Vitals. They chose a page with high traffic and conversion to ensure meaningful results. During the testing period, 50% of visitors were directed to the optimized page (version A), while the other 50% were sent to the original page (version B). The only difference between the two versions was that version A was optimized for Core Web Vitals, and there were no other changes.


Version A demonstrated faster loading speeds on mobile, with a 0.4-second improvement in load time and almost no layout shift. This resulted in an impressive 92.72% improvement in Cumulative Layout Shift (CLS) compared to version B. Additionally, First Input Delay (FID), First Contentful Paint (FCP), and Time to First Byte (TTFB) all improved by 7.95%, 8.45%, and 18.03%, respectively.


When Rakuten 24 compared the optimized version A to the unoptimized version B, they found that A Brings About:

  • 53.37% increase in revenue per visitor
  • 33.13% increase in the conversion rate
  • 15.20% increase in average order value
  • 9.99% increase in the average time spent.
  • 35.12% reduction in the exit rate.


Optimizing web performance can be difficult yet rewarding. By utilizing a data-driven approach, Rakuten 24 has achieved both an improved user experience and a noticeable positive effect on their business. Recognizing that this is just the beginning, they are committed to continuing to enhance their website to offer customers more delightful experiences.

Rakuten 24 encourages developers to collaborate and not go it alone when it comes to optimization. By exchanging their experiences, goals, and successes, developers can leverage Core Web Vitals data to foster an understanding between team members and stakeholders and together strive for a superior user experience and increased business growth.

Boost You Website Speed With Website Speedy Tool

To speed up the entire website optimization process, refer to our Saas-based website optimization tool, "Website Speedy," which instantly reduces your website loading times by 3x. All you have to do is to register yourself, add the website speedy script and the let our tool work on your website speed and core web vitals!


  • Core Web Vitals
  • Lazy Loading
  • Page Speed
  • Mobile Optimization
Background Image of Review Section

Test your Website Speed now

You can quickly analyze your site just by entering the site address in the input below! Find your current speed with Google page insights and instantly fix it to grow your sales and Conversion rate!

Claim Your Free Demo Now

One of our Experts will get in touch with you to provide a complete Performance Audit of your website and help you resolve the issues that are slowing down your website and growth

Website Speedy may use the information you provide to contact you about our products and services. You may unsubscribe at any time. For more information, view our Privacy Policy.