In combination with video content transmitted by a video streaming service, additional content may also be displayed to viewers. The video streaming service may provide a framework that allows the additional content to be provided by third parties. By allowing third parties to develop and provide additional content, the range of interactions and experiences made available through such content may, in some cases, be significantly expanded. The additional content may be displayed inside a respective assigned area, such as an inline frame (Iframe), embedded within a web page or other interface in which the video content is displayed. Additionally, techniques may be provided for controlling focus between a video player that displays the video content and the embedded area that displays the additional content, for example to help ensure that user input is provided to its intended target.