What happens if I don't enable RLS on a Supabase table?

Without RLS enabled, any authenticated user (using the anon key) can SELECT, INSERT, UPDATE, or DELETE any row in the table via the Supabase JavaScript SDK. There is no automatic per-user filtering. This is a critical data exposure vulnerability in multi-user applications — one user can trivially read another user's data simply by querying the table without any filters. Always enable RLS on every table that stores user data, before the table goes to production.

What is the difference between permissive and restrictive RLS policies?

Permissive policies (the default) are combined with OR logic — if any permissive policy grants access to a row, the user can access it. Restrictive policies (created with AS RESTRICTIVE) are combined with AND logic — a row must satisfy ALL restrictive policies AND at least one permissive policy. Use restrictive policies for hard constraints like subscription tier gating that should never be overrideable by other policies. Most policies should be permissive; restrictive policies are for exceptional, compliance-level constraints.

How do I write an RLS policy for a table that doesn't have a user_id column?

Use a JOIN or subquery to link the table to a related table that does have a user_id. For example, if you have a comments table linked to a posts table which is linked to users, your SELECT policy might use: USING (EXISTS (SELECT 1 FROM posts WHERE posts.id = comments.post_id AND posts.user_id = auth.uid())). Alternatively, restructure your schema to add a user_id column (possibly redundant with the FK chain) for simpler, faster RLS policies. The join approach is correct but ensure join columns are indexed to avoid performance issues.

Can the service role key bypass RLS, and is that safe?

Yes, the service_role key completely bypasses all RLS policies — it operates as a superuser from PostgreSQL's perspective. This is intentional and necessary for administrative operations (migrations, background jobs, cross-user analytics). It is safe as long as the service_role key is never exposed to browser code. Store it as a server-only environment variable (never use the NEXT_PUBLIC_ prefix), use it only in server-side code, and rotate it immediately if you suspect it has been leaked. The anon key, by contrast, is designed to be safe in the browser because RLS protects the data.

How do I test that my RLS policies are actually working correctly?

Create two separate test user accounts in your Supabase project. Insert rows as User A (via your app or the dashboard insert). Then log into your app as User B and attempt to query the same data — either through your app UI or by using the Supabase JS client in the browser console. The query should return zero rows. In the Supabase SQL editor, you can simulate a user's context using SET LOCAL role = authenticated and setting the JWT claims to test policies directly. For automated testing, create a test Supabase project and write integration tests that create users, insert data, and verify isolation programmatically.

Engineering·9 min read·June 20, 2026

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The Vulnerability You Ship Without RLS

When you create a table in Supabase and start building your app, there is a default behavior that surprises most developers when they discover it in production: without Row Level Security enabled, every row in your table is accessible to every authenticated (and sometimes anonymous) user via the Supabase JavaScript SDK.

Consider a SaaS application with a documents table where each row belongs to a specific user. Without RLS, any client-side call like this returns every document in the table — across all users:<

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