Abstract: Systems and methods enable users to browse purchasable items and conduct payment and purchasing transactions within the a single UI environment of a host application, without navigating to a separate application to complete the transaction. Purchase of purchasable items can be implemented using a computing device. A first user interface can be generated, including purchasable item listings. The purchasable item listings can be received by the computing device. A single host application displays the first user interface including the purchasable item listings on a display. A second user interface based at least in part on a user selection can be generated including a purchase and/or payment web page. The purchase and/or payment web page can be received by the computing device. The single host application can display the second user interface, as well. A payment transaction can proceed based on purchase information input into the one or more input fields.