What is Row Level Security (RLS) in Supabase and why does it matter?

Row Level Security (RLS) is a PostgreSQL feature that Supabase exposes to control which rows a user can access in a database table. Without RLS policies enabled, any user with the anon key can read, insert, update, or delete all rows in a table through the Supabase REST API. RLS policies act as WHERE clauses that are automatically appended to every query, ensuring users only access data they are authorized to see. Enabling RLS on every table is considered a fundamental security requirement when building with Supabase. UNPWNED checks whether your Supabase project has RLS enabled and flags tables that are publicly accessible without policies.