Page speed scores for mobile are usually lower than desktop. That’s because PageSpeed Insights (PSI) simulates the page load conditions of a low-end device on slow 4G network throttling for mobile. These conditions represent roughly the bottom 25% of 4G connections and top 25% of 3G connections, which means the performance score a site gets from PSI does not necessarily equate to the real world experience your users will have when visiting your site.