How to deploy Netlify relay for custom traffic routing

If you’ve ever needed a lightweight way to proxy traffic through Netlify’s global edge network, you’ve likely run into the limitations of standard redirects. Most developers try to force Netlify to act as a transparent proxy using basic configuration files, only to find that it doesn't handle complex request forwarding or specific protocol requirements. That’s where using a dedicated Netlify Edge Function relay comes into play.

The netlify-relay project is a clean, efficient way to handle this. Instead of relying on heavy server-side infrastructure, you’re offloading the heavy lifting to Netlify’s edge nodes. This is particularly useful when you need to mask your backend origin or route traffic through a specific domain structure without managing a full-blown VPS proxy.

The critical configuration trap

Here is where most people get tripped up: the TARGET_DOMAIN environment variable. If you don't include the port number in your environment variable, the relay will fail silently or throw connection errors. Netlify’s environment configuration is strict, and the relay logic expects a fully qualified URL including the port.

If your target is https://example.com, you must set the variable to https://example.com:443. If you omit the :443, the underlying fetch request in the Edge Function will default to an incorrect protocol or port, leading to a 502 or 404 error. Don't assume the system will infer the port for you.

Deployment best practices

While you can fork the repository, I strongly recommend downloading the source and deploying it as a fresh project. Forking keeps your repository tethered to the original, which creates unnecessary noise in your GitHub history and makes it harder to manage your own custom tweaks.

1. Initialize your project: Use the Netlify CLI to link your local directory. It’s faster and gives you better control over environment variables.
2. Set the environment: Use netlify env:set TARGET_DOMAIN "https://your-domain.com:443" --scope functions --context production.
3. Verify the target: Before you even push, run a curl -I against your target domain. If your backend isn't responding correctly to a standard header request, the relay won't magically fix it.

Troubleshooting common failure modes

If you’re seeing connection refused errors, the issue is almost always at the origin. Check your firewall settings to ensure the port you specified is actually open to the public internet. Netlify’s edge nodes need to reach your server; if you’re behind a restrictive firewall that only allows specific IPs, you’ll need to whitelist the Netlify Edge IP ranges.

Another common point of failure is the SNI (Server Name Indication) configuration. If your backend expects a specific SNI header, ensure your client configuration matches the domain you’ve set in the relay. If you’re still seeing issues, check the Edge Function logs directly in the Netlify dashboard. They provide the most granular view of where the request is dying.

This approach is a robust way to handle traffic routing without the overhead of traditional server management. Once you have the TARGET_DOMAIN set correctly and your origin port open, the system is remarkably stable. Try this today and share what you find in the comments, or read our breakdown of Netlify Edge Functions performance next.