A method of providing an ad extension includes selecting an advertisement for display. The method also includes selecting additional information related to the advertisement. The method also includes transmitting data representing the advertisement to a browser. The browser interacts with an expandable API to render an inline frame having an advertisement slot. The browser renders and displays the advertisement in the frame. The method also includes transmitting display data representing the additional information related to the advertisement to the browser. The browser receives an input to activate the ad extension. In response to the input, the browser interacts with the expandable API system to expand and render the frame. The browser renders, in the frame, the advertisement slot containing the advertisement. The browser also renders, in the frame, the additional information. The browser displays the expanded inline frame, such that the displayed frame covers a portion of the content.