Next.js request.url Returns Internal Proxy URL on Containerized Platforms

Problem

When deploying Next.js to Railway, Vercel, or similar containerized platforms,

request.url

in Edge runtime or API routes can return the internal proxy URL (e.g.,

http://localhost:8080

) instead of the public domain (e.g.,

https://example.com

).

This causes

NextResponse.redirect(new URL(path, request.url))

to redirect users to the internal URL, which fails with

ERR_CONNECTION_REFUSED

.

Context / Trigger Conditions

• Symptom: Browser shows

  ERR_CONNECTION_REFUSED

  to

  localhost:8080

  or similar
• Console errors:

  Failed to fetch RSC payload

  followed by connection refused
• Network tab: Shows 307 redirect to

  https://localhost:8080/...

• Environment: Next.js deployed to Railway, Vercel, Docker, or any reverse proxy setup
• Code pattern: Using

  new URL('/path', request.url)

  for redirects

Solution

Replace

request.url

with an environment variable for the public URL:

// Before (broken on containerized platforms):
return NextResponse.redirect(
  new URL(`/not-found?code=${shortCode}`, request.url)
);

// After (works everywhere):
const baseUrl = process.env.NEXT_PUBLIC_APP_URL || "https://example.com";
return NextResponse.redirect(
  new URL(`/not-found?code=${shortCode}`, baseUrl)
);

For reusable code, create a helper:

const getBaseUrl = () =>
  process.env.NEXT_PUBLIC_APP_URL || "https://example.com";

Verification

1. Deploy the fix to production
2. Visit a URL that triggers the redirect
3. Verify the redirect goes to the public domain, not localhost
4. Check browser console for absence of

   ERR_CONNECTION_REFUSED

Example

File:

app/[shortCode]/route.ts

// Add helper at module level
const getBaseUrl = () =>
  process.env.NEXT_PUBLIC_APP_URL || "https://clicktowa.com";

export async function GET(request: NextRequest, { params }) {
  const { shortCode } = await params;
  const baseUrl = getBaseUrl();

  // ... lookup logic ...

  if (!link) {
    // Use baseUrl instead of request.url
    return NextResponse.redirect(
      new URL(`/not-found?code=${encodeURIComponent(shortCode)}`, baseUrl)
    );
  }

  // ... rest of handler
}

Notes

• This issue occurs because containerized platforms route traffic through internal load balancers/proxies. The

  request.url

  reflects the internal connection, not the original public request.

• Some platforms set headers like

  X-Forwarded-Host

  or

  X-Original-Host

  , but these aren't automatically used by

  request.url

  .

• The

  NEXT_PUBLIC_

  prefix makes the variable available in both client and server code, which is appropriate for the public URL.

• Always provide a sensible fallback in case the env var isn't set.

• This also affects

  request.headers.get('host')

  in some configurations—always prefer explicit environment variables for public URLs.

Related Patterns

• Auth callback URLs should also use

  NEXT_PUBLIC_APP_URL

• OAuth redirect URIs need the public domain
• Sitemap and robots.txt generation should use the env var
• OpenGraph and canonical URLs should use the env var

References

• Next.js Environment Variables
• Railway Networking