EventNet is the largest video event ontology existent today, consisting of 500 events and 4, 490 event-specific concepts systematically discovered from the crowdsource forum like WikiHow. Such sources offer rich information about events happening in everyday lives. Additionally, it includes automatic detection models for the constituent events and concepts using deep learning with around 95K training videos from YouTube. In this demo, we present several novel functions of EventNet: 1) interactive ontology browsing, 2) semantic event search, and 3) tagging of user-loaded videos via open web interfaces. The system is the first in allowing users to explore rich hierarchical structures among video events, relations between concepts and events, and automatic detection of events and concepts embedded in user-uploaded videos in a live fashion. Categories and Subject Descriptors I.2.10 [ARTIFICIAL INTELLIGENCE]: Vision and Scene Understanding—Video Analysis Keywords EventNet Ontology Brow...