The tech industry is in the middle of a massive, uncontrolled social experiment. Having made commercial mass surveillance the economic foundation of our industry, we are now learning how indiscriminate collections of personal data, and the machine learning algorithms they fuel, can be put to effective political use. Unfortunately, these experiments are being run in production. Our centralized technologies could help authoritarians more than they help democracy, and the very power of the tools we’ve built for persuasion makes it difficult for us to undo the damage done. What can concerned people in the tech industry do to seize a dwindling window of opportunity, and create a less monstrous online world?