Certain services provided together with, or in support of, relevant core platform services of the gatekeeper, such as identification services, web browser engines, payment services or technical services that support the provision of payment services, such as payment systems for in-app purchases, are crucial for business users to conduct their business and allow them to optimise services. In particular, each browser is built on a web browser engine, which is responsible for key browser functionality such as speed, reliability and web compatibility. When gatekeepers operate and impose web browser engines, they are in a position to determine the functionality and standards that will apply not only to their own web browsers, but also to competing web browsers and, in turn, to web software applications. Gatekeepers should therefore not use their position to require their dependent business users to use any of the services provided together with, or in support of, core platform services by the gatekeeper itself as part of the provision of services or products by those business users. In order to avoid a situation in which gatekeepers indirectly impose on business users their own services provided together with, or in support of, core platform services, gatekeepers should also be prohibited from requiring end users to use such services, when that requirement would be imposed in the context of the service provided to end users by the business user using the core platform service of the gatekeeper. That prohibition aims to protect the freedom of the business user to choose alternative services to the ones of the gatekeeper, but should not be construed as obliging the business user to offer such alternatives to its end users.