Exposure to media content across one or more media delivery mechanisms is measured. The delivery mechanisms can include, for example, television and radio, as well as Internet delivery of web pages or other content viewed on a computer, mobile device, or other electronic device using a browser or other application. Media can include web-based content and/or audio content originating from a network source and/or from other content sources. Reference signatures are generated for media content items of interest. Monitoring devices and/or software monitor user exposure to media items, and intercepted signatures are generated. In some embodiments, user exposure across multiple delivery mechanisms is monitored. Reports can be generated based on comparison of the intercepted signatures with the reference signatures; such reports may include analysis of media exposure across multiple delivery mechanisms. Content items can be selected for presentation to a user based on media exposure history.