A Supabase/PostgreSQL feature that controls which database rows each user can see or modify.
Row Level Security (RLS) is a Database feature that enforces access control at the row level. Instead of protecting entire tables, RLS lets you specify which rows specific users can access. A user might see only their own posts, or admins might see all posts.
RLS policies are SQL conditions that filter rows. The database automatically applies them — if a Query would return rows a user should not see, they are silently filtered out. RLS checks Authentication status and JWT tokens to identify users and enforce policies.
The silent filtering is what makes RLS tricky to debug: your loader returns an empty array with no error, and the console shows nothing wrong. The Network Tab in DevTools reveals a 200 Status Code with an empty [] response — this is the classic RLS symptom. Use Logging to confirm data is empty before suspecting RLS, then check your policies in the Supabase dashboard.
RLS is crucial for security in multi-user apps. Without it, you must rely on application code to check permissions — easy to accidentally leak data. With RLS, Supabase and PostgreSQL prevent unauthorized access at the deepest level.
RLS works through RLS Policies — individual rules attached to each database table that grant or deny permissions for SELECT, INSERT, UPDATE, and DELETE operations.
RLS is a form of Authorization at the database level — it ensures users can only access the data they're permitted to, regardless of what the frontend code does.
RLS policies work alongside database triggers, which can bypass RLS using the service role for automated system actions like creating notifications.
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