According to Google, best practice is to aim for a three-second load time between SERP and page. They also said, though, that most sites come nowhere near that mark. After analyzing 900,000 mobile ad landing pages spanning 126 countries, Google found that over 70% took almost seven seconds to fully display visual content above the fold.

Mobile sites lag behind desktop sites in a number of key engagement metrics, such as pages per visit, bounce rate and average time on site. For retailers this can be particularly costly, because 30% of all online shopping purchases now occur on mobile devices.