Fix a Blank Page or 404 After Deployment With AI

Reproduce the Problem on the Live URL

Open the deployed website or web app and reproduce the problem.

Check what happens

The homepage is completely blank A page works until you refresh it, then shows 404 Some routes return 404 The page loads but styles, images, or JavaScript are missing The project works locally but breaks only after deployment

Collect the Evidence

Collect the most useful evidence you can before you ask the AI assistant anything.

the live URL the exact page or route that fails any visible error message relevant browser console errors relevant runtime or deployment errors, if available

Keep this information ready for the next step.

IMPORTANT

Do not include passwords, API keys, tokens, or other secrets in anything you copy.

Diagnose the Production Problem Before Changing Anything

Open your AI coding assistant inside the project and give it the production error, or describe exactly what happens.

Find the Root Cause of the Broken Live Version

Analyzes the current project together with the production problem and returns the root cause, the evidence, whether the fix belongs in the project or the hosting configuration, and the smallest safe fix — without applying it yet.

This project works locally but has a blank page, 404 error, or broken routes after production deployment. Analyze the current project and the production problem before changing anything. Check specifically for: - incorrect SPA routing or missing production fallback - direct-route or page-refresh 404 problems - incorrect build output directory - incorrect Vite or framework base/public path - broken JavaScript, CSS, image, or asset paths - missing production environment variables - client-side runtime errors - incorrect project root or deployment configuration - differences between local development and the production build Determine the actual root cause from the project configuration and the error I provide. Do not redesign the project or make unrelated changes. First give me: 1. the root cause 2. the evidence 3. whether the fix belongs in the project or hosting configuration 4. the smallest safe fix Do not apply the fix yet. Live URL: [PASTE LIVE URL] Error or behavior: [PASTE ERROR OR DESCRIBE WHAT HAPPENS]

NOTE

For Vite projects, the production base option can affect the generated asset URLs. Single-page applications may also require hosting configuration that sends direct route requests back to the app instead of returning 404.

Fix Only the Confirmed Cause

Once the cause is confirmed, ask the AI assistant to fix only that problem.

Apply the Smallest Safe Fix

Changes only what the confirmed cause requires, runs the production build, checks the generated output, and reports what changed plus anything you still have to configure manually.

Apply the smallest safe fix for the production issue we identified. - change only what is required to fix the confirmed cause - preserve the existing design and functionality - do not add unnecessary dependencies - do not hard-code secrets - update routing, build, asset-path, or framework configuration only if required - clearly tell me if part of the fix must be made in the hosting dashboard After making the fix: - run the production build - check for build errors - verify the generated production output Then give me a short summary of what changed and anything I still need to configure manually. Do not deploy automatically.

If the problem is caused by a hosting setting rather than the project code, make the required change in your hosting dashboard before redeploying.

Redeploy the Existing Project

Redeploy the existing project, then open the live version again.

Your project Deployments

In your hosting dashboard

Apply any hosting setting the assistant told you to change Redeploy the existing project Open the live version again

Verify the Live Website or Web App

Check the live version against every item below before you call this fixed.

The homepage loads normally

Direct links to important routes work

Refreshing an internal route does not produce a 404

CSS and JavaScript load correctly

Images and other assets load

Important features still work

No new critical browser console errors appear

No important production requests fail unexpectedly

Test at least one internal page by opening its URL directly and refreshing it.

IMPORTANT

If the problem remains, collect the new production error or behavior and diagnose that result instead of repeating the previous fix.

The deployment is fixed when the live project works correctly through normal navigation, direct links, and page refreshes.