Provided herein are systems and methods of inserting video content. A media player can receive, from a primary video content server, a video content item including primary video content to be presented on a webpage. The video content item can be associated with an encoding specifying a content spot in the primary video content. The media player can, subsequent to initiating playing of the video content item, the encoding specifying the content spot within the video content item. The media player can generate a request for supplemental video content to play based on the parsing of the encoding. The media player can transmit, to a secondary video content server, the request. The media player can receive, from the secondary video content server, the supplemental video content item selected based on the request. The media player can play the supplemental video content item during the content spot on the webpage.