This article examines Google’s political-economic influence in the emerging ‘digital growth machine’ through two urban-tech initiatives, Fiber and Sidewalk Labs. The findings highlight the company’s dual role as both a platform and an infrastructure, its capacity for collaboration with local governments and its iterative, experimental use of urban environments. It argues that Google’s urban-tech power in cities is neither fixed nor easily defined; the company purposefully remains ambiguous in order to continually test and invest in new ventures, fuelled by the speculative ethos of Silicon Valley and the demands of venture capital. Using Google as a case study, the article calls for a broader theorisation of tech power in cities, focusing not just on economic heft but also on the ways that tech companies enlist other actors in speculative projects, and adapt, pivot and repurpose their products in response to local demands.