Supabase is an open-source Backend-as-a-Service (BaaS) platform built on PostgreSQL, providing instant APIs, authentication, real-time subscriptions, storage, and serverless functions. It combines the power of a traditional PostgreSQL database with modern BaaS features, offering a developer-friendly alternative to Firebase with the flexibility of SQL. The platform auto-generates RESTful APIs via PostgREST, supports Row Level Security for granular access control, and provides a complete ecosystem for building production-ready applications without managing backend infrastructure.