Request headers

Request headers carry information that is specific to the incoming request and its path taken to the application. Request headers are added by the HTTP handler service.

Request Headers

Fly-Client-IP

Client IP Address: The IP address of the client from the perspective of Fly Proxy. If you are using another reverse proxy service in front of the Fly.io platform, this header will be set to proxy service’s IP addresses, rather than the client making the request. In that case, you’ll need to parse the IP addresses in the X-Forwarded-For header to find the client IP address.

Fly-Forwarded-Port

Original connection port: This header is always set by the Fly Proxy and denotes the actual port that the client connected to the Fly edge node which is then forwarded to the application instance.

Fly-Region

Edge Node Region: This header is a three letter region code which represents the region that the connection was accepted in and routed from.

Not to be confused with the environment variable FLY_REGION, which is where the application is running.

X-Forwarded-For

Client and Proxy List: A comma separated list of IP addresses including the address of the client that originated the request and the addresses of the proxy servers the request passed through. For example, “77.97.0.98, 77.83.142.33” contains the client and the one proxy it passed through. On the Fly.io platform, the last address (rightmost) in this list will be a shared or dedicated IP address assigned to your app.

This header must be treated with caution to avoid spoofing attempts. Follow the directives in the MDN documentation for X-Forwarded-For to learn how parse the header safely. If you aren’t using another reverse proxy in front of the Fly.io platform, the Fly-Client-IP header might be a better choice to get client IP addresses.

X-Forwarded-Proto

Original client protocol: The protocol which the client used to make the request. Either http or https.

X-Forwarded-Port

Original connection port: This header may be set by the client and should denote the port that the client set out to connect to.

X-Forwarded-SSL

SSL Status: This indicates if the client connected over SSL. Its value can be either on or off.

Request and Response Headers

Via

Proxy Route: This header, added by proxies, shows the path taken, and protocols used, by the connection. MDN has full documentation for this header. For example, a connection through the Fly edge may show 2 fly.io in the field, denoting that version 2 of HTTP was used by the connection as it passed through the Fly Proxy.