Mobile-friendliness has been a cornerstone of SEO ever since Google officially made it a ranking factor in 2015. However, it is more critical than ever that you optimize your content for mobile devices, as Google rolled out mobile-first indexing in 2019. This means that the search engine looks primarily at the mobile version of a website when ranking content, as this is considered the “primary” version instead of the desktop version. This switch was not a surprise to many people, as it is estimated that nearly 75% of internet users will access the internet solely via mobile devices by 2025.