Case study
Documented public incidentDocumented: Lovable Google Login Redirects to localhost:3000
Based on publicly reported incidents with linked sources — not a fictional client narrative. Describes the real problem and how I fix the same pattern for paying clients.
Subject
Documented: Ishwar Rimal's Lovable + Supabase project (public write-up)
Stack
Lovable, React, Supabase Auth, Google OAuth
Outcome
Root cause = Supabase Site URL still on localhost; fix published Mar 2025
This case study documents a real, published troubleshooting story — not an anonymized client engagement. The pattern appears repeatedly in Lovable community threads and vendor playbooks; it is one of the most common calls I get.
The documented incident
Published: March 25, 2025 by Ishwar Rimal, Senior Frontend Engineer at Intuit, on Medium.
His setup: Lovable frontend + Supabase backend. He added "Sign in with Google."
What worked: Cloning locally and testing on localhost — Google login succeeded.
What failed: On the Lovable preview URL (preview-xyz.lovable.dev), clicking "Sign in with Google" always redirected to localhost:3000.
What he tried first: Updated Google Cloud Console — authorized JavaScript origins and redirect URIs. Still broken.
Actual root cause (his words): "The issue wasn't with Google or my code; it was with Supabase." The Site URL in Supabase Authentication → URL Configuration was still http://localhost:3000. After OAuth, Supabase sends users to Site URL — so every successful Google login landed on localhost regardless of Google settings.
His fix:
- Supabase → Authentication → URL Configuration → set Site URL to the Lovable preview URL.
- Add production/custom domains to Redirect URLs when deploying.
- Confirm Google Cloud has
https://<project>.supabase.co/auth/v1/callback.
The article has 6+ claps and remains a top search result for this exact error string.
How common is this?
Multiple independent sources describe the same failure mode:
| Source | Claim |
|---|---|
| Ishwar Rimal (Medium) | Preview works locally; preview URL redirects to localhost |
| RapidDevelopers OAuth guide | "Most common mistake is Site URL still http://localhost:3000" |
| Afterbuild Labs ERR-145 | "~15% of broken Lovable deployments" — three surfaces must align: Supabase Site URL, Google redirect URIs, client redirectTo |
The failure is silent: users see Google consent, click Allow, then hit a dead localhost URL — no obvious error in the app console.
Why custom domain makes it worse
The same pattern triggers when founders connect a custom domain: auth "worked on lovable.app" and breaks on yourdomain.com because Supabase Redirect URLs and Site URL were never updated. That is the production variant of Rimal's preview-URL bug.
How I fix this pattern (my engagement)
When a founder describes "Google login sends me to localhost," I don't start with more Lovable prompts. I align all three surfaces in one pass:
- Supabase Site URL + Redirect URLs (preview, production, custom domain with
/**wildcards). - Google Cloud (and GitHub, if used) callback URIs.
- Code audit for hardcoded
redirectTo: 'http://localhost:3000'in shared auth utilities — the layer Ishwar Rimal's story implies but doesn't always show in generated code.
Typical turnaround: same-day for a single-domain fix; $799 Priority Fixes when Stripe webhooks and env vars drifted at the same time.
What you should search to verify
lovable google login localhost supabaseishwar rimal lovable googlesupabase site url localhost lovable
Sources
- Fixing the "logIn with Google" issue in Lovable (Ishwar Rimal, Medium)
- Supabase Auth — Redirect URLs
- Lovable OAuth redirecting to localhost (Afterbuild Labs)
Same symptoms? Step-by-step fix guide or contact me.
Primary sources
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