This disclosure relates to displaying notifications for content items on a mobile device to a user. A processor receives meta-data associated with the content item and receives context data indicative of a current context of the mobile device. The processor then determines a first value based on the meta-data, the context data and historical data indicative of historical interactions with historical notifications that are based on the meta-data, the first value being indicative of a current likelihood of the user interacting with a notification that is based on the meta-data. Finally, the processor sends first output data based on the first value to an output module to allow selectively outputting the notification based on the current likelihood. By selectively outputting the notification based on the current likelihood the notification can be withheld until the user is likely to interact with the notification.