Digital technologies provide powerful new tools for covert influence strategies. The concept of ‘online manipulation’ has been used to describe a range of different practices, ranging from disinformation campaigns to targeted advertising and dark patterns. There is an emerging view in human rights scholarship that some of these practices may violate our right to freedom of thought. In this chapter, we argue that covert online influences undermine mental autonomy, and that the latter is protected by the right to freedom of thought. We propose that manipulative online practices interfere with freedom of thought when they affect one’s mental autonomy in a sufficiently global manner. We lay out a framework to establish when this threshold is reached, asking whether (1) the attempted influence or its originator was hidden, (2) the targeted person fell within a vulnerable category of individuals, or there existed an information or power asymmetry, (3) the attempted influence targeted a type of thought reaching a certain level of cogency, seriousness, cohesion and importance, or mental processes linked with core aspects of external autonomy; and (4) eventually considering the frequency and duration of the attempted influence.