This page is the introduction to the IDSA Rulebook, the International Data Spaces Association’s reference guide for creating, operating and growing data spaces. It is addressed to those who design, build, operate, regulate or take part in data spaces, and it separates mandatory requirements from optional, value-adding practices, with technical, commercial and legal guidance (including how it relates to the EU Data Governance Act and Data Act). It explains the normative language used in the document (“must”, “should”, “may”), sets out the ten principles of the Manifesto of International Data Spaces, such as “Your data, your choice” and “Data does not flow through the data space”, and positions IDSA among other key initiatives: ISO/IEC 20151, the Dataspace Protocol (DSP), the Decentralized Claims Protocol (DCP), the Eclipse Dataspace Working Group, the Eclipse Dataspace Components (EDC) and the Technical Compatibility Kit (TCK). It closes with the wider landscape (the Data Space Connector Report and the Data Spaces Radar) and how to contribute, as the Rulebook is published under a CC BY licence.