This disclosure provides various techniques that may allow for tracking how a user interacts with content. For example, a user may interact with various types of content, such as web pages, applications, text, multimedia, or any other type of content. In one example of web page content, for example, this disclosure provides that executable code may be included with a web page and run on a user's system (e.g., via a web browser). The code may be capable of monitoring which content is visible in a viewport of the web browser, when the content is visible, and what part of the viewport contains the content. This monitoring data may be used to measure user interaction or engagement with the content.