Reverse Proxy vs Forward Proxy

Both proxies sit between clients and servers, but they serve opposite purposes. A forward proxy acts on behalf of clients. A reverse proxy acts on behalf of servers. The difference matters for security, architecture, and performance.

The Key Difference

Forward Proxy: Client-Side

A forward proxy retrieves resources for a client. The client connects to the proxy, the proxy connects to the destination.

How It Works

1. Client requests example.com
2. Request goes to forward proxy first
3. Proxy evaluates request (allowed? cached?)
4. Proxy forwards request to destination
5. Destination responds to proxy
6. Proxy sends response to client

Common Use Cases

• Content filtering — Block malicious sites, adult content, or social media in corporate networks
• Anonymity — Hide client IP from destination servers
• Caching — Store frequently accessed content to reduce bandwidth
• Bypass restrictions — Access geo-blocked or network-restricted content
• Logging — Track employee internet usage

Example: Corporate Web Proxy

# Client browser configuration
Proxy: proxy.company.local:8080

# Request flow
User → Forward Proxy → Internet → Website
User ← Forward Proxy ← Internet ← Website

The destination website sees requests coming from the proxy's IP, not the user's.

Reverse Proxy: Server-Side

A reverse proxy accepts requests on behalf of servers. Clients connect to the proxy, the proxy routes to the appropriate backend server.

How It Works

1. Client requests api.example.com
2. Request hits reverse proxy
3. Proxy routes to appropriate backend (based on path, headers, load)
4. Backend processes request
5. Proxy returns response to client

Common Use Cases

• Load balancing — Distribute traffic across multiple backend servers
• SSL termination — Handle HTTPS encryption at proxy, pass HTTP to backends
• Routing — Route /api to API server, /static to CDN
• Security — Hide backend server IPs, block DDoS, WAF
• Caching — Cache static content for faster delivery
• Compression — Gzip responses before sending to clients

Example: NGINX Reverse Proxy

server {
    listen 443 ssl;
    server_name example.com;
    
    # SSL termination
    ssl_certificate /etc/letsencrypt/live/example.com/fullchain.pem;
    ssl_certificate_key /etc/letsencrypt/live/example.com/privkey.pem;
    
    # Route API requests to backend
    location /api/ {
        proxy_pass http://10.0.0.2:3000;
        proxy_set_header Host $host;
    }
    
    # Serve static files directly
    location /static/ {
        root /var/www;
    }
    
    # Route everything else to web app
    location / {
        proxy_pass http://10.0.0.3:8000;
    }
}

Clients only see example.com. They don't know about the backend servers at 10.0.0.2 and 10.0.0.3.

Side-by-Side Comparison

Forward Proxy Scenario

Context: Corporate network with internet filtering.

• Employees must use proxy to access internet
• Proxy blocks access to social media, malware sites
• External sites see corporate proxy IP, not individual employee IPs
• IT can log and audit all outbound requests

Reverse Proxy Scenario

Context: Web application with API and frontend.

• Single domain (app.example.com) serves multiple services
• SSL certificate installed once on proxy
• Backend servers run plain HTTP (simpler, faster)
• Proxy load balances across 3 API servers
• DDoS attacks hit proxy, not backend

Can They Coexist?

Yes. A network can have both:

Client → Forward Proxy → Internet → Reverse Proxy → Backend Server

• Forward proxy: Corporate network controls outbound access
• Reverse proxy: Your server infrastructure controls inbound access

Choosing the Right One

Use Forward Proxy When:

• You control the clients (employees, devices)
• You want to filter or log outbound traffic
• You need to hide client IPs from destinations
• You want to cache outbound content

Use Reverse Proxy When:

• You control the servers (web apps, APIs)
• You want to load balance across backends
• You need SSL termination in one place
• You want to hide backend server IPs
• You need to route requests based on path/headers

Popular Software

Forward Proxy

• Squid — Industry standard, caching, filtering
• Dante — SOCKS proxy server
• tinyproxy — Lightweight HTTP proxy

Reverse Proxy

• NGINX — Most popular, high performance
• HAProxy — Advanced load balancing
• Traefik — Cloud-native, auto-discovery
• Caddy — Automatic HTTPS, simple config
• Apache — Traditional, feature-rich

Next Steps

• Set up SSL certificates on your reverse proxy
• Secure your server behind the proxy
• Tune NGINX for high traffic