TL;DR. 42501 permission denied for table … means the role has no grant on the table. Postgres stops the request before any RLS policy even runs. From 30 October 2026 Supabase stops granting new tables in public automatically on existing projects, so every table you create after that answers 42501 until you grant it. The fix is three statements together - a grant, enable row level security and a policy. Grant alone without RLS and the table is open to everyone.

I built a free Supabase security checker that reads the grants on every exposed table. Most projects have too many grants. 42501 is the other side, too few. So I reproduced it locally to see what really happens.

What does 42501 mean?

It's the Postgres code for insufficient privilege. Before a client touches a table Postgres checks two layers. Grants decide if the role can run the operation at all. RLS policies decide which rows it sees. A missing grant fails first and loud, as an error.…