Algorithm-based decisions are having an increasing impact on our daily lives. Whether we book a flight, apply for a job, apply for a loan or look for a life partner on an internet platform - it is often not clear that on the other side a machine is setting the price, pre-selecting applicants, assessing creditworthiness and looking for a partner. Online retailers are trying to extract the maximum willingness of their customers to pay by setting individualised prices based on algorithms. In some countries, criminal courts rely on software to assess the tendency of criminals to reoffend. These examples show that the use of algorithms raises a wide range of questions, some of which are of a legal nature, but also have links to ethics, economics and technology.