Systems and methods of measuring the visibility of overlay content in a display of a computing device are provided. A page renderer can identify a position of a video block with respect to a web page rendered on the client device, identify a portion of the web page visible in a viewport of the client device, identify a portion of the video block visible in the viewport, and pass data identifying the portion of the video block visible in the viewport to an element renderer. The element renderer can receive the data, identify a position of overlay content with respect to the video block, compare the position of the overlay content to the portion of the video block visible in the viewport to determine visibility of the overlay content in the viewport, determine whether the visibility meets a visibility threshold, and provide visibility data to a records server.