Drawing on the experience of recognised experts from across a range of different fields and jurisdictions, this landmark publication tackles default rules in private law in comparative perspective. Often underestimated, but highly influential, default rules are non-mandatory rules that kick in where nothing else has been agreed or provided.The contributions explore default rules from a variety of angles relevant to both scholarship and legal practice, including: - behavioural aspects and the role of platform terms in the digital age; - the remit and operation of defaults in different areas, ranging from contract and commercial law to succession, civil procedure and private international law; - a comparison between Common law and Civilian approaches as well as the EU level; - the perspectives of different 'players' engaged in the generation and application of default rules.