Active Choice Interventions at Scale: Browser Defaults under the Digital Markets Act

Can active choice mitigate preset-default effects? Implementing a difference-indifferences design around the EU Digital Markets Act’s choice-screen mandate, we find that choice screens increased Firefox usage by 91 percent on iOS and by 13 percent on Android, relative to a no-mandate counterfactual. The gap in effect size between iOS and Android is consistent with the fact that choice screens on Android primarily reached new devices, whereas it also reached existing users on iOS.