With the most recent updates of its mobile operating systems, in April 2021 Apple implemented a new global App Tracking Transparency policy. The policy obliges app developers to display an additional (Apple-designed) prompt to request permission from end users for the developer to “track” the user, even when the user has already consented to the sharing of its data through the developer’s own consent tool. Apple presents the new policy as a step to enhance privacy. Others, including the authors of this article, see it as a “bombshell for third-party mobile ad tech” that, together with Google’s disabling of third-party cookies, only entrenches the data supremacy of Apple and Google, and forecloses data-based competition and consumer choice across the entire Apple ecosystem. These concerns in fact have already triggered an investigation by the French Autorité de la concurrence and a complaint of eight media and tech associations before the German Bundeskartellamt. From the standpoint of EU law, this article describes the relevant conduct and technicalities, its impact on end users’ data privacy and on competition, and how both interests may be weighed considering the existing legislation.