Among other things, one or more techniques and/or systems are provided for annotating content based upon user reaction data and/or for maintaining a searchable content repository. That is, a user may request and/or opt-in for user reaction data to be detected while a user is experiencing content (e.g., watching a movie, walking through a park, interacting with a website, participating on a phone conversation, etc.). Metadata associated with the content may be used to determine when and/or what sensors to use to detect the user reaction data (e.g., metadata specifying an emotional part of a movie). The content may be annotated with a reaction annotation corresponding to the user reaction data, which may be used to organize, search, and/or interact with the content. A search interface may allow users to search for content based upon annotation data and/or aggregated annotation data of one or more users who experienced the content.