An app is an application that is primarily designed and developed for the mobile sector. If apps are used as a media channel, they function as an advertising medium, for example for adverts. This requires a user-friendly interface, high performance, personalised content, transparent labelling of advertising content and comprehensive measurement to enable effective marketing campaigns. Brand-specific apps with a high reach are suitable for this, as well as apps that can be cross-brand, cross-industry or cross-topic, such as for news, reference works, translations, dating, health and medicine, learning, navigation, music and audio.