Why page speed (performance) is important?

Google cares about page speed (site performance) more than ever before. Site performance has a direct effect on your business metrics: search ranking, amount of bounced visitors, conversion rate (source: Test My Site by Google).

Google measures performance through the dedicated Performance Score. Performance Score is a ranking factor for search and ads results (source: Google, Jan 14, 2019 ).

Performance Score is determined by a tool named Lighthouse simulating a page load and analyzing the derived lab data. 100 is the best possible score which represents the 98th percentile, a top-performing site. A score of 50 represents the 75th percentile. A score of 90–100 is considered fast, and 50 to 90 is considered average. Below 50 is considered to be slow.

A high-performance site:

• Improves site position in search engine results (source: Google ).
• Decreases the number of bounced visitors (source: Pingdom ).
• Increases the number of site pages viewed during every session (source: Section ).