This paper develops principles for a democratically legitimate form of digitalisation. It goes further than a need for an ethics of digitalisation. Ethics is a relationship between all persons. Democratic legitimacy is a relationship between citizens who share a democracy and, therefore, elect governments and make laws together. Digital technologies have become a part of the infrastructure of contemporary democracies. They are a part of how parties, parliaments and publics debate, deliberate and communicate; how they form opinions; and how they give and demand accounts and justifications needed for public control. Digital technologies have transformed how governments and representatives contest elections; how they structure voter choice; how they compete; how they reach out to different pools of voters in the hope of aggregating them into winning electoral coalitions. Standards of democratic legitimacy are not just important for those who regulate digital technologies. They also need to answer further questions. First what should consumers who are also citizens demand of social media and digital platforms? When should they complain, feel outraged, question the reputation or credibility of providers; or, where it is possible, take their custom elsewhere? Second what norms should providers internalise and enforce upon themselves if we are to believe them when they claim to contribute to democracy? Third where are democracies justified in demanding autonomy and non-interference by outsiders: both in any substantive rules democracies choose to regulate digitalisation and in the procedures they use to define the do’s and don’ts of digital governance?