Can behaviour on social media predict future purchase patterns? Can what we click on social media foresee which political party will we vote for? Can the information we share on our wall foretell the next series I might want to watch? Can the likes on Instagram and Facebook predict the time one will spend on digital platforms in the next hour? The answer is no longer science fiction. It points to the ability of mainstream social media platforms such as Facebook and Twitter to be able to deliver specialised advertising services to highly targeted audience segments controlled by the billions of devices that flood our daily lives. At the same time, it highlights a more relevant problem: can social media guide, suggest or impose a certain behaviour or thought? Everything seems to indicate that they can do it. Predictive Technology in Social Media comprises 10 essays that reflect on the power of the predictive technology of social media in culture, entertainment, marketing, economics and politics. It shows, from a humanistic and critical perspective, the predictive possibilities of social media platforms, as well as the risks this entails for cultural plurality, everyday consumption, the monopolistic concentration of the economy and attention, and democracy. The text is an invitation to think, as citizens, about the unbridled power we have ceded to digital platforms. A new voice to warn about the greatest concentration of communicative power ever seen in the history of humanity.