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

A developer built LeakPatrol, a free read-only security scanner that checks AI-generated Supabase apps for leaked service_role keys, publicly exposed .env files, missing security headers, and tables readable without authentication. The tool's writeup argues the Supabase anon key is safe to ship in frontend JavaScript because access is governed by Row Level Security, while the service_role key bypasses RLS entirely and leaks everything if bundled via VITE_, NEXT_PUBLIC_ or REACT_APP_ variables. It also flags permissive using (true) policies, public storage buckets, and SECURITY DEFINER views as common leak vectors in apps built with Lovable, Bolt, v0 or Cursor.

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. Supabase gives every project two kinds of key: | Key | Starts with | Where it belongs | |---|---|---| | anon / publishable | eyJ... role anon or sb publishable | The browser. Fine to ship. | | service role / secret | eyJ... role service role or sb secret | Only on a server. Never in the browser. | 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. 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. 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. 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. Two quieter ones: with security invoker = on . SECURITY DEFINER service role , sb secret , sk- and sk live . You should find none. true . using true in your policies. If you'd rather not do it by hand, I built LeakPatrol https://www.getleakpatrol.com/?ref=devto , 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.