In one embodiment, a method includes obtaining a link to a video program; obtaining metadata that relates to the program and that defines, for a specified time point in the program, annotations to be invoked at the specified time point; wherein the annotations comprise: a graphic image; one or more filters, each of the filters comprising a key and one or more matching values; and optionally a reference to a video segment, an electronic document, program code statements, or a programmatic call; during playing the video, detecting that the video program is playing at the specified time point; in response to the detecting: for each particular annotation for the specified time point, retrieving a current value for the key, and causing to display the graphic image associated with that particular annotation only when the current value of the key matches one of the matching values of one of the filters.