Masader is a metadata catalog for Arabic NLP datasets, providing structured information about over 100 datasets including their tasks, dialects, sources, volumes, and licensing. The repository combines a Jekyll-based static site with a modular JavaScript frontend to enable dataset discovery through search, filtering, statistics visualization, and a natural language chatbot interface. While the core asset is the dataset metadata (JSON files in /datasets/), the web interface and associated tools (annotation, migration, validation scripts) form an application layer that makes the catalog usable and maintainable. The system supports dataset exploration via faceted search, demographic charts, and embedding-based clustering, with a chatbot for conversational queries. Metadata is kept up-to-date through migration scripts that handle schema evolution and validation checks that ensure consistency with external sources like venue links and volume totals.