Using Nginx as Reverse Proxy

In many deployments:

• Nginx handles incoming HTTP/HTTPS traffic
• Gunicorn runs your Flask app

Why use Nginx?

• HTTPS termination (TLS)
• better performance for static files
• request buffering
• security headers
• reverse proxy routing

High-level flow

diagram Diagram mermaid

  flowchart LR
  U[Users] -->|HTTPS| N[Nginx]
  N -->|HTTP| G[Gunicorn]
  G -->|WSGI| F[Flask App]

Minimal Nginx config (conceptual)

nginx

server {
    listen 80;
    server_name example.com;
 
    location / {
        proxy_pass http://127.0.0.1:8000;
        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header X-Forwarded-Proto $scheme;
    }
}

Static files

Often you configure Nginx to serve /static/ directly.

That reduces load on Gunicorn.

Common gotcha

If you build absolute URLs, make sure Flask knows it’s behind HTTPS.

Forwarded headers (X-Forwarded-Proto) and proper proxy settings matter.