Many online platforms are designed to facilitate transactions between buyers and sellers of goods and providers and recipients of services. To that end, platforms establish and enforce their own rules, policies, and mechanisms. However, how they (can) go about that is regulated by law. In this Chapter, we assess the scope for establishing and enforcing platform rules through the means of private law in the Netherlands. Under Dutch private law, the enforcement by platforms of their rules can simply be accomplished with ordinary means of contract law, combined with the de facto power mechanisms at the disposal of platforms (eg control over payments, management of review and reputational instruments, exclusion from participation/membership, termination of contract). However, these means are subject to review by courts whenever platform participants, via either individual or collective actions, contest the actions of the platform. In this Chapter, we describe and critically assess the current state of Dutch law by (i) providing an overview of the relevant legal framework in the area of private law; and (ii) reviewing the case law concerning the private law regulation of online platform contracts, rules, and activities. Accordingly, we will discuss how online platform regulation is affected by the default or mandatory rules applicable to specific contracts (eg agency, brokerage, and services more generally), general terms and conditions, unfair commercial practices, precontractual information duties, and e-commerce. We will not be concerned with case law in the domains of administrative law, competition law, criminal law, labor law or tax law. The resulting assessment charts the scope for online platforms to set their own rules and policies for transactions regarding goods and services in the Netherlands.