# Replit Deployment Not Working: Diagnose in Order

A Replit app that works in Preview but fails after publishing usually has an environment, command, port, Secret, storage, or deployment-type difference.

Canonical URL: https://truborankai.com/blog/replit-deployment-not-working

## Quick Answer

Make Preview work first, then read publishing logs and verify build and run commands, production Secrets, a long-running server bound to `0.0.0.0`, the configured port, and a homepage that answers the health check promptly. Use Static only for static output; apps with server behavior need a suitable deployment type. Compare production callbacks, databases, CORS, and storage separately.

## AI Summary

This guide follows Replit’s official publishing troubleshooting order. It distinguishes build failure, health-check failure, live 404, missing Secrets, wrong deployment type, ephemeral files, and production-only integration errors.

## Quick Questions

### Why does Replit Preview work but deployment fail?

Production can use different Secrets, commands, host and port requirements, deployment type, persistent services, callbacks, and filesystem behavior.

### Which host should my server bind to?

Replit’s current publishing guide says web servers must listen on `0.0.0.0`, not only localhost or `127.0.0.1`.

### Why do uploaded files disappear?

Replit documents that the published app filesystem is not persistent. Store durable data in a database or supported storage service.

## Main Explanation

Start with Preview. If the app does not run at its preview URL, deployment is not the first problem. Fix the run command, dependencies, application exception, port, or missing development Secret before publishing again.

When publishing fails, read the earliest meaningful log line. Confirm that the build command creates the expected output and the run command starts the application rather than exiting. Avoid asking Agent to rewrite commands until you know what the framework requires.

Check production Secrets in the Publishing pane. Editor Secrets do not automatically prove production has the same values. Missing database URLs, API keys, callback secrets, or environment flags can cause blank pages, failed login, and server errors. Never paste secret values into public logs or prompts.

Verify host, port, and health behavior. The server must listen on `0.0.0.0`. If `.replit` declares ports, its local and external mapping must match the process. The homepage should respond quickly enough for the deployment health check; move expensive startup work behind a request or cache it appropriately.

Choose the deployment type by runtime. Static works for generated HTML, CSS, and JavaScript without server behavior. API routes, server authentication callbacks, database work, and long-running logic need a server-capable option such as the appropriate Autoscale or Reserved VM configuration.

If publishing succeeds but the URL is broken, compare production dependencies, database access, CORS, OAuth and payment redirects, and file paths. Local files written during Preview will not provide durable production storage. Test direct route refreshes and mobile behavior.

After the application is stable, verify public discovery. Check status codes, HTTPS, canonical URLs, robots.txt, sitemap.xml, and anonymous content. Run TruboRankAI on the live Replit or custom domain; deployment success does not by itself make the site indexable.

## Practical Steps

1. Make the Preview URL work.
2. Read the first actionable publishing log.
3. Verify build and run commands.
4. Add required production Secrets securely.
5. Bind the server to 0.0.0.0 and verify ports.
6. Choose a deployment type that matches the runtime.
7. Compare production callbacks, storage, database, and CORS.
8. Audit the final public URL after recovery.

## FAQ

### Why does my Replit deployment return 404?

Possible causes include wrong build output, route fallback, run commands, port mapping, or a deployment type that does not match the app. Use logs and direct route tests.

### Can a slow homepage fail deployment?

Yes. Replit states that the health check can fail when the homepage takes more than five seconds to respond.

### Should a backend app use Static Deployment?

No. Static deployment is intended for static assets. Server behavior requires a compatible server deployment.

## Related Internal Links

- [Replit Agent Loop Recovery](/blog/replit-agent-stuck-in-loop)
- [Replit Agent Free Plan](/blog/replit-agent-free)
- [Vibe-Coded Site Not Showing in Google](/blog/vibe-coded-website-not-showing-in-google)
- [Audit the Published App](/ai-seo-audit-tool)