Online platforms are defined as intermediaries for the economic exchange of goods and services. They aim to connect users with each other so that contracts can be concluded between them. This article discusses how the largest online platform in Poland, i.e. Allegro, works. It discusses the conditions for the participation of users, the available modes of concluding contracts on Allegro, the course of the transaction and its implementation, the feedback system (rating system), the dispute resolution methods offered by Allegro, the additional guarantees for buyers offered by Allegro and the possibility of blocking or cancellation of a user's account by Allegro. The scope of regulation (by Allegro) of relations between Allegro users leads to a reduction in the scope of application of the provisions of the Polish Civil Code. The online platform offers buyer-friendly internal legal solutions that are designed to function much more efficiently and effectively than the institutions of applicable law. In this way, users can effectively pursue their claims via Allegro without having to rely on the support of the state apparatus to enforce their claims.