In this chapter we analyse the widely influential American Academy of Pediatrics’ (AAP) “screen time” guidelines (issued in 1999 and updated in 2016) in relation to the existing evidence about parental mediation and the lived experience of families in the digital age. In our interviews with 73 diverse families in London, we have been struck by how often some version of these guidelines surfaces, often without knowing where they come from, as parents castigate themselves for allowing their children “too much” screen time, without much critical examination of what this means. We argue that these and similar time- or exposure-based guidelines rely on an insufficient evidence base, and lead parents to prioritise restrictive forms of screen time that neither serve the purpose of keeping children safe, nor of helping them towards opportunities.