Published: March 17, 2021
By running an A/B test specifically focused on optimizing Web Vitals, Vodafone found that a 31% improvement in LCP led to 8% more sales, a 15% improvement in their lead to visit rate, and a 11% improvement in their cart to visit rate. [Vodafone](https://www.vodafone.com/) is a leading telecommunications company in Europe and Africa operating fixed and mobile networks in 21 countries and partnering with mobile networks in 48 more. By running an A/B test on a landing page (where version A was optimized for Web Vitals and had a 31% better LCP score in the [field](https://www.searchenginejournal.com/google-explains-why-field-data-is-more-reliable-than-lab-data/372404/) than version B), Vodafone determined that optimizing for Web Vitals generated 8% more sales. 31~%~ A 31% improvement in LCP led to... ~+~8~%~ Increase in total sales ~+~15~%~ Uplift in the lead to visit rate ~+~11~%~ Uplift in the cart to visit rate ## Highlighting the opportunity Vodafone knew that faster websites generally correlate to improved business metrics and were interested in optimizing their Web Vitals scores as a potential strategy for increasing sales, but they needed to determine exactly what kind of ROI they would get. ![Two screenshots of the Vodafone website.](https://web.dev/static/case-studies/vodafone/image/two-screenshots-the-voda-cf6f5c699cd1f.png) Some example screenshots of Vodafone's website. Note that these are **not** version A and version B from the A/B test. Both versions were visually and functionally identical. ## The approach they used ### A/B test The traffic for the A/B test came from different paid media channels, including display, iOS/Android, search, and social. 50% of the traffic was sent to the optimized landing page (version A), and 50% was sent to the baseline page (version B). Version A and version B both got around 100K clicks and 34K visits per day. As mentioned before, the only difference between version A and version B was that version A was optimized for Web Vitals. There were no functional or visual differences between the two versions other than that. Vodafone used the [`PerformanceObserver`](https://developer.mozilla.org/docs/Web/API/PerformanceObserver) API to measure LCP on real user sessions and sent the [field data](https://www.searchenginejournal.com/google-explains-why-field-data-is-more-reliable-than-lab-data/372404/) to their analytics provider. ![A diagram of the A/B test setup.](https://web.dev/static/case-studies/vodafone/image/a-diagram-the-b-test-se-427b18e78b906.png) ### Optimizations Vodafone made the following changes on the optimized page (version A): - **Moved the rendering logic for a widget from client-side to server-side** , which resulted in less [render-blocking JavaScript](https://developer.chrome.com/docs/lighthouse/performance/render-blocking-resources) - **Server-side rendered** critical HTML - **Optimized images** , including [resizing](https://developer.chrome.com/docs/lighthouse/performance/uses-responsive-images) the hero image, [optimizing SVG images](https://jakearchibald.github.io/svgomg/), using media queries to [avoid loading images](https://web.dev/articles/browser-level-image-lazy-loading.md.txt) that weren't yet visible in the viewport, and [optimizing PNG images](https://web.dev/blog/squoosh-v2.md.txt) ## Overall business results After optimizing version A for Web Vitals and comparing it to the unoptimized version B, Vodafone found that version A led to: - An 8% increase in sales - A 15% improvement in the lead to visit rate (the number of users who became a lead versus the total number of visitors) - An 11% improvement in the cart to visit rate (the number of users who visited their cart versus the total number of visitors) ![An illustration that reiterates the business results.](https://web.dev/static/case-studies/vodafone/image/an-illustration-reiterat-d99bc1eace701.png) The following table shows the values for `DOMContentLoaded` ("DCL") and LCP that Vodafone observed on version A ("Optimized Page") and version B ("Default Page"). Note that DCL actually *increased* 15%. The absolute values related to business metrics have been redacted. ![Optimized Page had a DCL of 4.05s and a LCP of 5.7s. Default Page had a DCL of 3.52s and a LCP of 8.3s.](https://web.dev/static/case-studies/vodafone/image/optimized-page-had-dcl-c0741c916019c.png) > > At Vodafone, we test new solutions, measure results, keep what worked and question what didn't, > learning from mistakes. We call it "Experiment, Learn Fast". Thanks to the collaboration with Google > and the introduction of LCP as the main KPI for page performance, it was possible to > significantly improve the customer experience of our e-commerce. > Davide Grossi, Head of Digital Marketing, Business