Where a provider of online intermediation services itself offers certain goods or services to consumers through its own online intermediation services, or does so through a business user which it controls, that provider might compete directly with other business users of its online intermediation services which are not controlled by the provider, which might give the provider an economic incentive and the ability to use its control over the online intermediation services to provide technical or economic advantages to its own offering, or those offered through a business user which it controls, which it could deny to competing business users. Such behaviour could undermine fair competition and restrict consumer choice. In such situations, in particular, it is important that the provider of online intermediation services acts in a transparent manner and provides an appropriate description of, and sets out the considerations for any differentiated treatment, whether through legal, commercial or technical means, such as functionalities involving operating systems that it might give in respect of goods or services it offers itself compared to those offered by business users. To ensure proportionality, this obligation should apply at the level of the overall online intermediation services, rather than at the level of individual goods or services offered through those services.