Enable proxy_ssl_server_name for Nginx HTTPS Backends

Proxying to an HTTPS backend in Nginx? Don’t forget this one directive:

location / {
    proxy_pass https://backend.example.com;
    proxy_ssl_server_name on;  # This one
}

Why it matters: modern web servers host multiple SSL sites on one IP using SNI (Server Name Indication). When your Nginx proxy connects to https://backend.example.com, it needs to tell the backend “I want the cert for backend.example.com.”

Without proxy_ssl_server_name on, Nginx doesn’t send the SNI header. The backend doesn’t know which SSL cert to use, and you get connection failures or wrong cert errors.

When you need it:

• Proxying to Cloudflare-backed sites
• Proxying to shared hosting
• Any backend with multiple domains on one IP

Think of it like calling a company with multiple departments — you need to tell the receptionist which one you want, not just dial the main number.