Bolt.new Preview Not Working? Common Causes

If the Bolt.new preview is not working, the issue can be in the generated app, the dependency setup, the browser session, the run command or an external service call that fails as soon as the app loads. Do not assume the whole project is lost. Start by finding where the preview stops.

Check whether the preview is blank, stuck or showing an error

A blank preview usually points to a runtime error, missing route, failed import or app crash. A stuck loading state may mean the app is waiting for an API or database response. A visible error message may point to a dependency, module or build problem.

If the same project also fails after deployment, use the wider Bolt.new app repair service page for diagnosis.

Open the browser console

The console is often the fastest clue. Look for missing modules, undefined variables, failed imports, CORS errors, blocked requests and runtime exceptions. Read the earliest meaningful error first. Later warnings may only be side effects.

Check package and dependency problems

Bolt.new can generate an app that needs packages, versions or scripts to line up correctly. If an AI fix added a new library, check whether it was installed, imported correctly and compatible with the rest of the project. Dependency errors often appear as a broken preview before you ever reach deployment.

Check run commands and generated structure

A preview can fail when the expected command, framework structure or entry file does not match the generated project. Check whether the app has the right scripts, whether the main route exists and whether any generated files refer to components that were later moved or renamed.

Check external services that load on start

If the app contacts Supabase, an API or an auth service immediately, a bad environment variable or blocked request can make the preview look broken. For Supabase-specific faults, see Bolt.new Supabase not working.

Avoid broad reset prompts

Asking Bolt.new to rebuild the whole preview can create more changes than needed. A better repair prompt names the exact console error, the route, what changed recently and what should not be rewritten. If the preview gives only a blank screen or vague runtime error, isolate the first failure before changing more code.

Checklist

• Confirm whether the preview is blank, stuck or showing a specific error.
• Inspect console and network errors.
• Check recently added packages and imports.
• Check the run command and app entry points.
• Check services that load on startup.
• Compare preview behaviour with live behaviour if deployed.

Conclusion

A broken Bolt.new preview is usually a clue, not a verdict. Treat it as a debugging problem: observe the first failure, isolate the layer and repair the specific cause.

Check what changed before preview broke

Preview problems often appear after a package change, a new component, an auth prompt, a database feature or a broad instruction to clean up the app. Check the most recent change first. If the preview broke immediately after adding an integration, inspect that integration before rewriting unrelated screens.

It also helps to test one route at a time. If one page crashes and another still loads, the app is not universally broken. That usually points to a route, component or data call that can be isolated.

What not to do next

Avoid asking for a complete redesign or full app rebuild just to fix a preview error. That creates more moving parts and makes the original fault harder to find. Keep the repair narrow: the route, the error, the file or component, and the behaviour that should remain unchanged.