Microsoft has released an open-source tool that helps teams learn ontology design before choosing a knowledge graph platform. It is called Ontology Playground. The project is a fully static React app, which means it does not need a backend, account system, database, or hosted service to run. The goal is simple: Help people understand what goes inside a graph before they buy or build the graph database. Ontology Playground includes six pre-built domain ontologies: → Retail → Healthcare → Finance → Manufacturing → E-Commerce → Education Each one gives users a starting point for understanding entities, relationships, properties, and how domain knowledge gets structured. The app also includes a live visual designer, structured learning paths, hands-on labs, and RDF/XML export for Fabric IQ. Because it is static, it can be deployed almost anywhere. No backend. No vendor lock-in. No platform commitment upfront. This matters because many teams jump into knowledge graphs too early. They focus on the database first. But the harder question is usually: What should the graph actually know? Ontology Playground teaches that layer first.