Advances in AI are transforming the economy. Behind this wave of visible innovation lies a less visible but significant trend: the role of large technology firms – commonly referred to as ‘big techs’ – across the AI supply chain. This column analyses the AI supply chain and the market structure of every input layer, highlighting the economic forces shaping the provision of AI and the role of big techs in each input market. The authors illuminate challenges that big techs pose to consumer choice,