Custom domain returns ERR_CONNECTION_CLOSED while deployment URL works

Help
1

Current behavior

I have a Vercel project where the deployment URL works correctly, but the custom domain does not fully load.

Affected custom domains:

Working deployment URL:

On the custom domain:

  • browser shows net::ERR_CONNECTION_CLOSED
  • HTML/CSS/JS do not finish loading
  • the page becomes blank/gray

Expected behavior

The custom domain should fully load the same content as the working deployment URL.

Code, configuration, and steps to reproduce

Project:

  • Next.js static site on Vercel

DNS:

Vercel dashboard shows:

What works:

What fails:

  • full body transfers on the custom domain stall or close
  • browser shows net::ERR_CONNECTION_CLOSED

Important evidence:

  • Range requests work
  • Compressed responses work
  • Full normal GET on the custom domain hangs
  • The deployment URL for the same build works correctly

This suggests a custom-domain edge delivery / response streaming issue rather than DNS, TLS, or app code.

I can attach:

  • vercel-debug.txt
  • browser screenshot with ERR_CONNECTION_CLOSED

If needed, please escalate this to the infrastructure / edge team.

2

Additional evidence:

  • HEAD requests succeed
  • full body downloads stall
  • Range requests succeed
  • compressed responses succeed
  • deployment URL works
  • custom domain fails with ERR_CONNECTION_CLOSED

This looks like a custom-domain edge/body-streaming issue, not DNS or app code.