Is your Supabase anon key safe in the frontend? Yes. Here's what isn't.

If you've built an app with Lovable, Bolt, v0 or Cursor on top of Supabase, you've probably opened DevTools, seen a long eyJ... key in your JavaScript, and felt your stomach drop.

Good news first: that key is supposed to be there. Here's what it actually does, and the four things that do leak data in AI-built Supabase apps.

The anon key is public by design

Supabase gives every project two kinds of key:

The anon key just identifies your project. On its own it grants nothing: what someone can do with it is decided entirely by your Row Level Security (RLS) policies.

That's also the catch. The anon key is safe only if RLS is doing its job.

1. Tables with RLS turned off

With RLS off, anyone who copies your anon key out of your JavaScript can read, and often write, the whole table with a single request. No login needed.

Check every table in the SQL editor:

select tablename, rowsecurity
from pg_tables
where schemaname = 'public';

Anything showing false is open. Turn it on and add a policy that ties rows to their owner:

alter table public.profiles enable row level security;

create policy "Users read their own profile"
on public.profiles for select
using (auth.uid() = user_id);

Watch out for policies with using (true). They turn RLS on but let everyone through, which AI tools sometimes generate to "fix" a permissions error.

2. The service_role key in the browser

The service_role (or sb_secret_) key bypasses RLS completely. If it's in your frontend, every table is open no matter how good your policies are.

AI tools usually put it there by accident: a VITE_SUPABASE_SERVICE_ROLE_KEY or NEXT_PUBLIC_... variable, added to make an admin feature work. Anything prefixed VITE_, NEXT_PUBLIC_ or REACT_APP_ is bundled into the JavaScript every visitor downloads.

If you find it: rotate the key in Supabase (Settings → API) right away, then move the admin work into an Edge Function that reads the key from Supabase secrets.

3. Storage buckets

Storage has its own policies, separate from your table RLS, and they're easy to forget. A "public" bucket means anyone with a file's URL can download it. Fine for avatars, not for invoices, ID photos or exports.

In Storage, check which buckets are public, and give private ones policies on storage.objects, just like tables.

4. Views and functions that skip RLS

Two quieter ones:

• Views run with their creator's rights by default, so a view over a protected table can expose it. On Postgres 15+, create them with with (security_invoker = on).
• Functions marked SECURITY DEFINER also run with their owner's rights. If one is callable through the API, check it only returns what the caller should see.

The 2-minute check

1. Open your live app, then DevTools → Sources, and search for service_role, sb_secret_, sk- and sk_live. You should find none.
2. Run the SQL above. Every table should show true.
3. Look for using (true) in your policies.
4. Check which storage buckets are public.

If you'd rather not do it by hand, I built LeakPatrol, a free read-only check that looks for leaked keys, a public .env and missing security headers, and, once you prove you own the site, which Supabase tables can be read without logging in. Each finding comes with a prompt you can paste back into your AI tool to fix it.

The anon key was never the problem. What you've built around it is what counts.