Supabase connection failures, empty query results, and auth errors are common problems with Lovable-built apps. Here is how to diagnose and fix each one.
When a Lovable app misbehaves with data, the cause is often in the Supabase layer rather than the front end.
The symptoms cluster into a few patterns: the app cannot connect at all, queries return empty even though data exists, or authentication fails or silently logs users out.
Understanding which pattern you are seeing is half the fix. Each has a distinct, well-known root cause.
This guide walks through diagnosing connection issues, Row Level Security problems, and auth failures in that order.
Work through them methodically and most Supabase-related bugs in a Lovable app resolve quickly.
Start with the simplest cause: wrong or missing credentials. If the app cannot reach Supabase at all, this is usually why.
Confirm the Supabase project URL and the public anon key are correct and match the project Lovable is using. A typo or a stale key breaks everything.
Make sure you are using the anon key on the client, not a secret or service-role key, and not a key from a different project.
If you recently changed Supabase projects or rotated keys, update them everywhere the app references them.
A quick test: hit the Supabase project from its dashboard or a simple request to confirm the project itself is up and the credentials are valid.
If you connect fine but queries come back empty while data clearly exists in the dashboard, Row Level Security is the prime suspect.
RLS restricts which rows each user can see. If RLS is enabled but no policy grants access, every query returns nothing, with no obvious error.
Open the table in the Supabase dashboard and check its policies. Confirm there is a policy that allows the intended read for your authenticated users.
A common Lovable scenario: tables are created with RLS on but policies are incomplete, so the web app works under one assumption while another client gets blocked.
Add or correct the policy so the right users can read and write, then retest. Empty results usually vanish once policies match intent.
Auth problems show up as failed logins, 401 errors, or users getting logged out unexpectedly.
First confirm the auth settings in Supabase match how the app signs users in. Check which providers are enabled and whether email confirmation is required.
If email confirmation is on and users have not confirmed, their sign-in will fail in ways that look like a bug. Decide whether confirmation should be required and configure accordingly.
For 401 errors on data calls, the issue is often that requests are not carrying a valid session token, so Supabase treats them as anonymous and RLS blocks them.
Ensure the authenticated session is established before making protected queries, and that the token is attached to those requests.
Auth flows that involve email links or OAuth depend on correctly configured URLs. Misconfiguration here breaks sign-up and password reset.
In Supabase auth settings, confirm the Site URL and the allowed redirect URLs include the domains your Lovable app actually runs on, including your deployed and custom domains.
If a confirmation or reset link sends users to the wrong place or is rejected, an out-of-date redirect list is usually why.
When you add a custom domain to your Lovable app, remember to update these URLs in Supabase to match.
Keeping the URL configuration in sync with where your app is hosted prevents a whole class of confusing auth failures.
Stop guessing and let the data tell you. Both Supabase and your app surface information that points straight at the problem.
In the Supabase dashboard, review the logs for failed requests, policy denials, and auth errors. These often state the cause plainly.
In the browser, open developer tools and watch the network and console output when the failing action runs. The status codes and error bodies are diagnostic gold.
A 401 points to auth or token issues; an empty 200 result points to RLS; a connection error points to credentials or the project being down.
Matching the symptom to the log evidence turns a vague bug into a specific, fixable one.
If you also built a native iOS client against this Supabase backend, know that some failures are specific to that client.
The web app and the native app are separate clients. A bug in one does not always reproduce in the other, even on the same backend.
On iOS, decoding errors are common when your Swift Codable models do not exactly match the table columns, especially with snake_case, dates, and optionals.
Also confirm the native app attaches the auth session to requests, since a missing token produces the same RLS-driven empty results you might see on the web.
Debug the iOS client on its own terms, using Xcode's console alongside the Supabase logs, rather than assuming the web fix automatically applies.
You can avoid most of these issues with a short discipline before shipping.
Keep credentials correct and never leak secret keys into client code. Verify the anon key and project URL whenever you change environments.
Enable Row Level Security deliberately and write explicit policies for every table, then test with a real authenticated user, not just the dashboard.
Keep auth providers, email confirmation settings, and redirect URLs in sync with where your app is actually hosted.
Finally, check logs early when something breaks. The answer is usually sitting in the Supabase or browser console, waiting to be read.
Almost always Row Level Security. If RLS is enabled without a policy granting access, queries return nothing silently. Add a policy that allows your authenticated users to read the table, then retest.
The request likely is not carrying a valid session token, so Supabase treats it as anonymous and blocks it. Ensure the user is authenticated and the token is attached before making protected queries.
Check the Site URL and allowed redirect URLs in Supabase auth settings. They must include your deployed and custom domains. Update them whenever you change where the app is hosted.
Not always. They are separate clients on the same backend. iOS often has its own issues, like Codable models not matching columns or a missing auth token, that you must debug in Xcode independently.