How to Use proxy_set_header in Nginx for Proxy Configuration

Use the proxy_set_header directive inside an Nginx location or server block to set or override HTTP headers sent to the proxied server. This helps pass client information or control headers like Host and X-Forwarded-For when Nginx acts as a reverse proxy.

Syntax

The proxy_set_header directive sets or overrides HTTP headers sent to the proxied server. It takes two arguments: the header name and the value to set.

It is used inside location, server, or http blocks.

nginx

proxy_set_header header_name header_value;

Example

This example shows how to use proxy_set_header to forward the original Host header and client IP address to the backend server.

nginx

server {
    listen 80;
    server_name example.com;

    location / {
        proxy_pass http://backend_server;
        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    }
}

Output

When a client requests http://example.com/, Nginx forwards the request to http://backend_server with headers:
Host: example.com
X-Real-IP: <client IP>
X-Forwarded-For: <client IP plus any existing forwarded IPs>

Common Pitfalls

• Not setting Host header can cause backend servers to reject or misroute requests.
• Forgetting to forward client IP with X-Real-IP or X-Forwarded-For hides the original client IP.
• Using proxy_set_header outside allowed contexts causes configuration errors.

nginx

location / {
    proxy_pass http://backend;
    # Wrong: missing Host header
    # proxy_set_header Host $host;  # This line is missing
}

# Correct usage:
location / {
    proxy_pass http://backend;
    proxy_set_header Host $host;
}

Quick Reference

Directive	Purpose	Example Value
proxy_set_header Host	Sets the Host header sent to backend	$host
proxy_set_header X-Real-IP	Sends client IP to backend	$remote_addr
proxy_set_header X-Forwarded-For	Adds client IP to forwarded chain	$proxy_add_x_forwarded_for
proxy_set_header Connection	Controls connection header	"" (empty string to disable)

Key Takeaways

Use proxy_set_header inside location or server blocks to modify headers sent to backend servers.

Always set the Host header to preserve the original domain name for backend processing.

Forward client IP using X-Real-IP and X-Forwarded-For headers to keep client information.

Incorrect or missing proxy_set_header directives can cause backend errors or loss of client info.

proxy_set_header syntax is: proxy_set_header header_name header_value;