§4.4 Market definition in the presence of multi-sided platforms

94. Multi-sided platforms support interactions between different groups of users, creating a situation where the demand from one group of users has an influence on the demand from the other groups (127). In this situation, the reaction by one group to a change in supply conditions may also affect other groups, which gives rise to feedback loops between the different sides of the platform, that is to say to indirect network effects (128). Platforms typically internalise these indirect network effects between different groups when setting their supply conditions. 95. In the presence of multi-sided platforms, the Commission may define a relevant product market for the products offered by a platform as a whole, in a way that encompasses all (or multiple) user groups (129), or it may define separate (although interrelated) relevant product markets for the products offered on each side of the platform (130). Depending on the facts of the case, it may be more appropriate to define separate markets where there are significant differences in the substitution possibilities on the different sides of the platform. To assess whether such differences exist, the Commission may take into account factors such as whether the undertakings offering substitutable products for each user group differ, the degree of product differentiation on each side (or each user group’s perception thereof), behavioural factors such as the homing decisions (131) of each user group and the nature of the platform (for instance whether it is a transaction or a matching platform). In either case, the Commission takes into account, where relevant, the indirect network effects between user groups on different sides of the platform when defining the relevant markets or in the competitive assessment. 96. In practice, the presence of indirect network effects may render the assessment of demand substitution and, in particular, the application of the SSNIP test more challenging than in situations where no such demand interdependence between user groups exists. 97. Multi-sided platforms may supply a product to a user group at a zero monetary price, or even at a negative price, in order to attract users to products offered on the other sides of the platform and monetise their products on those sides. Zero monetary prices may be an integral part of multi-sided platforms’ business strategy. The fact that a product is supplied at a zero monetary price does not imply that there is no relevant market for that product. 98. In such cases, non-price parameters are particularly relevant for the assessment of substitution. The Commission focuses on factors such as product functionalities (132), intended use (133), evidence of past or hypothetical substitution (134), barriers or costs of switching, such as interoperability with other products, data portability and licensing features (135). The Commission may also consider alternatives to the SSNIP, such as assessing the switching behaviour of customers of the zero-price product in response to a small but significant non-transitory decrease of quality (‘SSNDQ’) (136).

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Source: EUR-Lex (Cellar) · retrieved 2026-09-07