The decade began with smartphones still being a new thing and ended with them being the primary computer for most of humanity. That single shift explains most of what the 2010s did to the world.
In January 2010 the iPhone was three years old. Android was growing but fragmented. Most people on earth had never touched a smartphone. The idea that billions of people would be carrying connected computers in their pockets within ten years was not yet settled consensus, even among people who worked in technology.
By December 2019 it was simply reality. More than three billion people had smartphones. Mobile internet access had arrived in places that had never had fixed internet infrastructure. The mobile phone had become the primary screen for social interaction, entertainment, navigation, photography, banking, and commerce for the majority of the human population.
The social media decade followed directly from that. Facebook went from four hundred million users in 2010 to two and a half billion in 2019. Instagram, Twitter, WhatsApp, WeChat, Snapchat and then TikTok all grew to billions of active users by leveraging the smartphone access that had not previously existed. The connectivity was genuinely new and in many ways genuinely positive. And it came with consequences that the decade ended without fully resolving: misinformation at scale, attention harvested as a commodity, algorithms optimised for engagement regardless of effect.
Cloud computing went from a niche infrastructure concept to the default architecture for almost everything built during the decade. AWS, Azure, and Google Cloud moved from interesting experiments to critical infrastructure. This made it far easier to start technology companies and far harder for any company to build infrastructure that could compete at scale.
Machine learning went from academic to applied. Image recognition. Voice assistants. Recommendation systems. Translation. The applications were consumer-facing by the end of the decade in ways they had not been at the beginning.
What the 2010s built was the substrate. The platforms, the infrastructure, the devices, and the habits of attention. The next decade would run on top of all of it, and inherit all the tensions that the 2010s had created but not resolved.