If your Lovable or Bolt app runs cleanly in the editor preview but fails, looks outdated, or loses features on its public URL, the cause is usually one of five things: the live site is an older version than the editor, the production build fails where preview did not, an environment variable is missing or in the wrong scope, the database or backend is not connected, or the hosting and domain setup is not serving the version you intended. Work through them in that order. Each check is quick, and each one rules out a whole class of problem before you rewrite any code.
The official Lovable and Bolt documentation describes these failure classes and their fixes, but neither platform publishes data ranking which cause is most common across projects. Treat the order below as a diagnostic sequence, not a frequency ranking.
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Why preview and the public site can behave differently
The editor preview and the published site are two separate things. Lovable’s hosting documentation describes the preview this way: “The preview is your live working view inside the editor: it updates as you build, and it can differ from what visitors see on the published site.” Bolt’s preview is also a development environment, and its troubleshooting guidance treats it as a different context from a production build.
That gap is where most “works in preview, breaks after deploy” reports come from. The preview runs the newest code you have written. The public URL runs whatever was last published, built, and served with the configuration available to it. A mismatch at any of those layers produces the same symptom: the app that worked on Tuesday in the editor is blank, stale, or missing features at the public address.
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The five causes and how to check each one
1. The live site is an older snapshot
Lovable publishes a snapshot of your project. Edits you make afterward do not reach the live site until you republish with Publish changes. This is the most common reason a public URL looks stale, and it is easy to miss because the editor keeps showing the newer version.
To check it, open the exact public URL in a fresh browser tab, then compare what it shows with the current editor state. If the editor has changes the public page lacks, click Publish changes and reload the public URL.
Accepting a draft in Lovable does not publish it. According to Lovable’s publish guide, accepting a draft joins those edits to your unpublished changes, and those still need to be published before visitors see them.
2. A production build error did not appear during preview
Preview tolerates some problems that a production build rejects. Bolt’s preview troubleshooting says that “Running a build surfaces compilation errors that may not appear during normal development, which can help pinpoint what’s preventing the preview from loading.” Run npm run build in the project to see the same compilation pass a deployment runs, and fix the first error it reports.
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Lovable handles this at the publish step. Its publish dialog shows a build error and withholds the publish action when the latest changes fail to build. Its troubleshooting guide lists four responses: examine the logs, ask Lovable to investigate, revert to the version before the issue, or plan the fix before rebuilding.
Read the exact error message before you act on it. Re-sending a vague prompt such as “fix the deploy” usually changes unrelated code and leaves the original compilation error in place. Copy the first error line, including the file name and line number, and address that specific problem.
3. A required environment variable is missing or in the wrong scope
Environment variables are the second most common source of a blank or broken published app. A variable that exists in your local setup may not exist in the deployed environment, or it may exist in the wrong scope.
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Lovable separates secrets into two scopes, and mixing them up is a common mistake:
- Build secrets are available while packages install and the app builds. A build-time token does not automatically become a runtime key.
- Project secrets are available to backend runtime code. A runtime secret will not authenticate a package installation or build step.
For each variable, confirm three things: the exact name (names are case-sensitive and must match the code), the value, and whether the code reads it at build time or at runtime. If a value is a private key, keep it on the server or in the platform’s secret store. Do not place it in client-side code, where any visitor can read it.
4. The database or backend is not connected
Hosting a frontend and running its backend are separate jobs. Lovable’s hosting guide distinguishes the pages it serves from its built-in backend, which provides a database, authentication, storage, and functions. A public site can load its interface while data, logins, or uploads fail, which can look like a deployment problem when the actual fault is a backend connection.
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When a feature fails on the public URL, check these items in order:
- The backend URL the app expects matches the backend you deployed against.
- The connection is authorized in your account settings.
- Row-level access rules or equivalent data permissions allow the request the app makes.
- The backend service itself is running and not reporting an incident.
5. Hosting, domain, or project limits block the intended deployment
Sometimes the code is correct and the deployment never reaches visitors in the form you intended. Check three things.
First, check the platform’s status page for an active incident. Bolt’s status page reports whether a service issue is in progress.
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Second, confirm the project is still published. In Lovable, if you use a custom domain, its status should read Live. The default lovable.app address can keep working while a custom domain is still being configured, so a page that loads on one address and not the other points to the domain setup rather than the app.
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Third, check for project size limits. Bolt’s publishing troubleshooting says a project must be under 100MB to publish, and it names large media files as a common reason for exceeding that cap. This limit applies to Bolt projects specifically. If your project is over the cap, remove unused images, video, or other media, or host those files externally and reference them by URL.
A page that loads but behaves incorrectly is different. For that symptom, the browser console and the failed network requests are more useful than a domain check, because they show whether the failure is in your code, your configuration, or the backend call.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Troubleshooting sequence
- Compare the live URL with the editor. Open the exact public address in a fresh tab. In Lovable, if the editor has newer changes, click Publish changes and reload.
- Check the platform status page. Look for an active incident before you debug your own code.
- Reproduce the failure and capture the console. Open the browser developer tools, reload the page, and record the first error in the Console tab and any failed request in the Network tab. For a white screen, the console message is usually the fastest clue.
- Run a production build. Run
npm run buildlocally or through the platform’s build check. Fix the first compilation error before attempting another deployment. - Verify variables and the backend. List every required variable, confirm its exact name and value, place each one in its build-time or runtime scope, then verify the database connection and permissions.
- Confirm domain and size limits. In Lovable, confirm the custom domain reads Live. In Bolt, confirm the project is under 100MB.
Lovable hosting or Bolt with Netlify
Bolt’s current guide makes Bolt hosting the default for new projects. It also documents Netlify as an alternative hosting route. Choosing between them does not solve an application error or a missing variable. The table below compares what you need to check on each path. Where the sources reviewed do not describe a detail, the cell says so.
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| Where the live version comes from | A snapshot published with Publish changes | Not stated in the sources reviewed; confirm the deploy source in Netlify |
| Build step and failure behavior | The publish dialog blocks publishing when the latest changes fail to build | Run npm run build locally to surface compilation errors; Netlify-side build behavior not stated in the sources reviewed |
| Variable scopes | Build secrets and project secrets are separate scopes | Not stated in the sources reviewed; check the variables your build and runtime each need |
| Backend and database | Built-in database, authentication, storage, and functions | Backend is typically a separate service, such as the Supabase connection described in Bolt’s integration guide |
| Domain and status | Custom domain status should read Live | Domain and provider status not stated in the sources reviewed; check the Netlify and Bolt status pages |
Whichever route you use, the diagnosis is the same. Compare the public version with the editor, check the build, verify variables and the backend, and then check the hosting layer.
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