The Hasura Schema Registry is a version control system for GraphQL schemas that helps developers detect breaking changes in APIs before they are released into production. It classifies changes as 'Breaking', 'Dangerous', and 'Safe' to provide an overview of the impact of each change. This tool is particularly useful for managing role-based schema changes and can be integrated with staging or pre-production environments to alert developers about worrisome schema changes. By using the Hasura Schema Registry, teams can ensure that their APIs remain coherent and reliable, reducing the risk of unexpected issues in production.