Short answer
Not necessarily. Turning on RLS is the first step, not the last. Check four things: that signed-out visitors don’t have permissions on tables they don’t need, that any view over a protected table follows the table’s rules, that no rule lets everyone read private data, and that the admin key (secret or service_role) never reaches the browser. Then test the rules by signing in as two different users.
What to check once RLS is on
01
Grants the anon role still has
“Adding policies doesn't take those grants back.” Supabase, Row Level Security
Policies decide which rows a role sees; table grants decide what it can do at all. A grant left in place can give signed-out visitors a way to insert rows that a policy alone doesn’t close. Revoke what the anon role doesn’t need.
02
Views that skip RLS
“A view over a protected table hands out every row its policies were meant to withhold” Supabase, Row Level Security
Views skip RLS by default, because they usually run as the postgres user that created them. A view over a protected table can return every row the table’s policies hold back. On Postgres 15 or later, Supabase’s guide shows how to make a view follow the policies of its tables. On older versions, revoke the anon and authenticated roles’ access to the view, or keep it in a schema the API doesn’t expose.
03
Policies that let everyone in
“Use it only for data that is meant to be public.” Supabase, Row Level Security
A select policy written as using (true) for the anon role gives every signed-out visitor read access to every row their grants already reach. That suits published content, and nothing personal.
04
A key that skips RLS entirely
“Never use a secret key in the browser or expose it to customers.” Supabase, Row Level Security
The secret or service_role key skips RLS by design, which is why Supabase says to keep it out of the browser. If it has been in front-end code, anyone who found it can get past the policies above, so replace it.
05
Policies nobody has tested
Supabase’s guide suggests a SQL test file per table under supabase/tests, run with supabase test db, that checks what each role can and can’t do. At the very least, sign in as two users and confirm neither can read or change the other’s rows.
Checked against the vendor’s docs on : Supabase docs: Row Level Security.
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Related: Free Supabase RLS policy checker · Free Supabase grants checker · Supabase service_role key exposed · Supabase anon key in frontend code · Supabase RLS fixes