Improving Core Web Vitals on the Mail.ru home page resulted in an average 10% increase in conversion rates

Where we started . Mail.ru is an important resource for many people. It receives several hundred million visits per month, and is a portal from where people can access email, news, social media, performance internet searches and more.

Mail.ru wanted to provide its visitors with a high quality user experience, so work began to improve Core Web Vitals. Before discussing our optimization strategy, a few technical details of the Mail.ru home page should first be noted.

Though the project had long been developed using our in-house templating engine in 2019.

CLS was one of the worst performing field metrics for the Mail.ru home page. Subsequent profiling of this page in the .

The return of SSR that can delay . We decided to use SSR for crucial content that the user will see on initial render, and offload rendering of hidden content on the client. At the moment, Mail.ru is experimenting with

To improve the perceived page load speed, work was required to decrease LCP and FID values. One way to achieve this is through .

For historical reasons, the widget is inserted at the very beginning of the page as a synchronously loading script. The share of polyfills in this script grew over time. To limit the negative performance effects of loading these polyfills, we implemented code splitting for both modern and legacy browsers.

We decided against the didn't target browsers that were modern enough for our needs. To address this, Mail.ru uses an in-house tool for identifying modern browser versions on the backend, and can adapt to those browsers accordingly.