Render "No Open Ports Detected" Deploy Error

How to fix it

Try these in order — the most common fix is first.

1. 1. Bind to 0.0.0.0 and PORT

   Copy steps
   1. Read process.env.PORT (Node) or os.environ['PORT'] (Python); default is 10000
   2. Listen on host 0.0.0.0, e.g. app.listen(PORT, '0.0.0.0')
   3. Redeploy and check logs for the listening message
   Did this fix it? Yes No

2. 2. Start listening earlier

   Copy steps
   1. Open the port first, then run migrations, cache warmup and other slow work
   2. Move one-off tasks to a pre-deploy command
   Did this fix it? Yes No

3. 3. Use the right service type

   Copy steps
   1. If the process serves no HTTP, create a Background Worker instead of a Web Service
   2. Remove duplicate server start from your start command or app code
   Did this fix it? Yes No

Symptoms

Deploy logs show "Port scan timeout reached, no open ports detected" or "No open ports detected on 0.0.0.0" and the deploy fails or hangs.

Why it happens

• Server binds to localhost or 127.0.0.1 instead of 0.0.0.0
• Server hardcodes a port instead of reading PORT
• Startup work takes too long before the server starts listening
• Two listeners conflict, or the service does not open a port at all (it is a worker)
• Server bound to IPv6 only (Render does not support IPv6)

This guide also covers

• render no open ports detected
• render port scan timeout reached
• render deploy failed port

The same problem in other apps

All export, render & quality loss guides →

• Railway Slow Deployments and Slow App (Railway)
• Fly.io Deploy Failed: Waiting for Depot Builder, Registry 401, Too Many Requests (Fly.io)
• Vercel Deployment Failed: Build Error (Vercel)
• DigitalOcean App Platform Build Failed (DigitalOcean)
• Heroku Build Failed Error (Heroku)

Other Render errors

• Render Free Instance Spins Down: Slow First Request
• Render Build or Service Out of Memory
• Render Build Failed: Exited With Status 1
• Render Free Postgres Expired or Deleted
• Render 502 Bad Gateway Error
• Render Custom Domain Verification or SSL Pending
• Render Health Check Failed or Deploy Timed Out
• Render Free Service Suspended: 750 Hours Used Up