Lovable App Won't Deploy to Production: Fix Guide 2026

Before You Start: 60-Second Triage

Open your published app in incognito mode (not your normal browser) with DevTools open (F12 on Windows, Cmd+Option+I on Mac). Incognito matters because cached state in your everyday browser can hide a production error, or fake one that is not really there. If you would rather hand this off, AppStuck specialises in Lovable app rescue and completion.

Check three panels, in this order:

1. Console tab: red errors tell you which file or variable is failing. “undefined is not an object” and “Missing Supabase environment variables” point straight at causes 1 and 2.
2. Network tab, Fetch/XHR filter: red rows are failing API calls. Look for calls going to localhost or returning 401/403, which point at causes 1 and 4.
3. Application, then Cookies: no Supabase auth cookie set on your production domain points at cause 4.

1. Environment Variables Exist in Preview but Not in Production

What it looks like: the preview runs fine, but the production build shows a blank screen or a console error like “Missing Supabase environment variables” or “supabaseUrl is required”. Network calls go nowhere or hit localhost.

Why it happens: Lovable apps are Vite projects. The preview sandbox injects your Supabase URL and anon key automatically, but the production deploy is a separate environment that does not inherit them. On top of that, Vite only exposes variables to the browser if they are prefixed with VITE_. A key named SUPABASE_URL will be silently undefined in the browser, while VITE_SUPABASE_URL works.

How to fix it:

1. List every variable your app reads. In the codebase, search for import.meta.env to find them all.
2. In your deploy target (Lovable’s own publish settings, or Vercel/Netlify if you connected one), add each variable with the exact same name, including the VITE_ prefix for anything used in the browser.
3. Redeploy. A new build is required, since Vite bakes these values in at build time, not at runtime. Changing a variable without rebuilding does nothing.
4. Verify in the incognito Network tab that your API calls now go to your real Supabase URL, not localhost.

“Audit every environment variable the app reads with import.meta.env. Confirm each one is prefixed with VITE_ for browser use, and list exactly which env vars I must set in my production deploy settings. Do not hardcode any keys in the source.”

When to call an expert: if you have set the variables, rebuilt, and the production build still cannot reach Supabase, the problem is usually a second config layer (a wrong project ref, or a key from the wrong Supabase project) that is faster to diagnose with someone reading the build logs with you.

2. Preview Works, Production Is a Blank White Screen

What it looks like: the home page is blank in production, or it loads but any refresh on a sub-page (like /dashboard) returns a 404 or a white screen. The preview never showed this.

Why it happens: two separate single-page-app traps. First, the deploy may be serving from the wrong output directory or with a wrong base path, so the browser downloads an empty shell. Second, Lovable apps use client-side routing, so the server must fall back to index.html for any unknown path. Without that rewrite rule, deep links and refreshes 404.

How to fix it:

1. Confirm the build output directory is dist (Vite’s default), not build, in your deploy settings.
2. Add an SPA fallback so all routes serve index.html. On Vercel this is a rewrite of /(.*) to /index.html; on Netlify it is a _redirects file with /* /index.html 200.
3. If the page is blank even at the root, check the Vite base setting. For a root-domain deploy it should be /. A leftover sub-path base is a common cause of an empty shell.
4. Verify by refreshing directly on a deep link in incognito. It should load, not 404.

3. The Build Fails Before the Site Even Loads

What it looks like: the deploy stops with a red build error. Common ones: “Type error”, “Cannot find module ‘./Header’”, or an out-of-memory crash on a large project.

Why it happens: the preview is forgiving; the production build is strict. The two failures we see most are TypeScript errors that the preview ignored, and case-sensitive import paths. macOS and the Lovable preview treat ./Header and ./header as the same file, but the Linux build server does not, so an import that worked locally fails in production.

How to fix it:

1. Read the build log top to bottom and find the first red error. Later errors are often caused by the first one.
2. For “Cannot find module”, check that the import path matches the file name exactly, including capitalisation.
3. For type errors, fix the type rather than disabling the check. If you must ship, you can set the build to not fail on type errors, but treat that as temporary debt, not a fix.
4. Re-run the deploy and confirm the build reaches “completed” before testing the live site.

When to call an expert: if the build fails with an error that does not name a file you recognise, or it passes locally but fails only on the deploy server, the gap is environmental and is usually faster to resolve with someone who reads CI logs daily.

4. The App Loads but Login Does Nothing in Production

What it looks like: the site is up, but signing in spins and returns you to the login page, or the magic link or OAuth redirect lands on an error. It all worked in the preview.

Why it happens: Supabase auth has an allowlist of redirect URLs and a Site URL, and they were configured for the preview domain, not your production domain. When the redirect comes back to a URL Supabase does not recognise, the session is never set.

How to fix it:

1. In your Supabase project, open Authentication, then URL Configuration.
2. Set the Site URL to your production domain (for example https://yourapp.com).
3. Add every production URL to the Redirect URLs allowlist, including the bare domain and any auth callback path your app uses.
4. If you use Google or another OAuth provider, add the same production callback URL in that provider’s console too.
5. Verify in incognito that after login a Supabase auth cookie is set on your production domain in the Application tab.

When to call an expert: auth bugs in production lock out real, paying users, and the failure is often a chain (Supabase plus the OAuth provider plus a custom domain). A 30-minute review usually catches the root cause faster than another guess.

5. Custom Domain Connected but Showing an Error or the Old Site

What it looks like: the .lovable.app URL works, but your custom domain shows a security warning, a “not found”, or a stale version of the site.

Why it happens: DNS changes take time to propagate, and the SSL certificate for a new domain is issued only after DNS resolves correctly. A mismatched record, or a record still pointing at an old host, is the usual culprit.

How to fix it:

1. Confirm the DNS records match exactly what your deploy host asks for. An A record or a CNAME pointing at the wrong target will not serve the right site.
2. Remove any leftover records from a previous host that conflict with the new ones.
3. Allow time for propagation. Use an incognito window or a different network to avoid your own cached DNS.
4. Once DNS resolves, confirm the host shows the SSL certificate as issued before testing the live domain.

When to call an expert: if DNS looks correct but the certificate never issues, there is usually a CAA record or a conflicting record blocking it that is quick to spot for someone who has done it many times.

6. Deploy Succeeds but Your Latest Changes Are Not Live

What it looks like: the deploy reports success, but the live site shows an older version, or your newest fix is missing.

Why it happens: either the deploy built from an older commit or branch, or a CDN and browser cache are serving the previous bundle. Vite filenames are content-hashed, so a true rebuild busts the cache, but a deploy that did not actually rebuild will not.

How to fix it:

1. Confirm the deploy built from the branch and commit that contains your change.
2. Trigger a fresh build rather than re-promoting a previous one.
3. Hard refresh in incognito (Cmd+Shift+R or Ctrl+Shift+R) to rule out a local cache.
4. Check the loaded JavaScript filename in the Network tab. If the hash changed, the new build is live.

When Self-Debugging Stops Making Sense

Most of the issues above are fixable with the steps provided. Some situations signal that continued self-debugging has diminishing returns:

• The same error returns after multiple fix attempts, which means the root cause has not been addressed.
• Security or data concerns (payments, personal data, anything regulated), where a professional review before launch is not optional.
• The launch has a deadline, where every hour of debugging has a direct cost (investor demo, customers waiting).
• The credits and hours already spent exceed what help would cost. A few hours of expert review often costs less than two days of credit loops.

Related Guides

• Lovable Troubleshooting Guide: Fix the 10 Most Common Errors (2026)
• Lovable platform overview, when a full rescue makes more sense than DIY

Frequently Asked Questions

Why does my Lovable app work in preview but not in production?
The preview sandbox injects environment variables and is forgiving about build errors and routing. Production is a separate, stricter environment. The most common gap is environment variables (especially Supabase keys) that exist in preview but were never added to your production deploy settings.

Why is my deployed Lovable app a blank white screen?
Usually one of two things: the deploy is serving the wrong output directory or base path so the browser gets an empty shell, or the single-page-app fallback to index.html is missing, so any route other than the exact root fails. Check the build output directory is dist and add an SPA rewrite rule.

Why does login work in preview but fail after I deploy?
Supabase auth only honours redirects to URLs on its allowlist. After deploying, set the Site URL and add your production domain to the Redirect URLs in Supabase Authentication settings, and update the callback URL in any OAuth provider you use.

Do I need to redeploy after changing an environment variable?
Yes. Vite bakes environment variables into the bundle at build time, not at runtime. Changing a variable without triggering a fresh build has no effect on the live site.

My build fails only on the server, not locally. Why?
The most common reason is case-sensitive imports. macOS treats Header and header as the same file, but the Linux build server does not, so an import with the wrong capitalisation fails only in production. TypeScript errors the preview ignored are the other frequent cause.

How long should a Lovable deploy take to go live?
A build is typically a few minutes. If you connected a custom domain, DNS propagation and SSL issuance can take longer, from minutes to a few hours, before the domain serves correctly with a valid certificate.

Can AppStuck fix a Lovable app that won’t deploy?
Yes. Deploy-stuck Lovable projects are one of the most common cases we handle. We start with a free 30-minute assessment, identify the root cause, and tell you what it takes to get to production before any work begins.