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Forward Proxy

A forward proxy sits between clients and the internet, making requests on behalf of clients. Corporate proxies (Squid, Zscaler) filter outbound traffic, enforce policies, and cache content. Clients must be configured to use the proxy. Forward proxies provide anonymity, content filtering, and bandwidth savings.

Definition

A forward proxy acts on behalf of clients – the client explicitly sends requests to the proxy, which forwards them to the destination server. The destination sees the proxy's IP, not the client's. Corporate environments use forward proxies to: enforce acceptable use policies (block categories of sites), inspect TLS traffic (SSL bump with CA injection), cache frequently accessed content (save bandwidth on repeated downloads), and log all web activity for compliance. Clients are configured via explicit proxy settings (HTTP_PROXY environment variable, browser proxy config, PAC files) or transparently via network interception (transparent proxy on the gateway). VPN services and Tor function as forward proxies – hiding client identity from destination servers. The key distinction from reverse proxy: forward proxy serves the client's interest, reverse proxy serves the server's interest.

Examples

  • –export HTTP_PROXY=http://proxy.corp:3128
  • –Squid: acl blocked dstdomain .gambling.com; http_access deny blocked
  • –PAC file: function FindProxyForURL(url, host) { return 'PROXY proxy:8080'; }

Related Protocols

http

Related Terms

NAT (Network Address Translation)

NAT translates private IP addresses to public IP addresses at a router boundary. NAT allows many devices to share one public IP. It breaks end-to-end connectivity – inbound connections require port forwarding. Carrier-grade NAT (CGNAT) adds another translation layer, complicating VoIP and gaming.

Reverse Proxy

A reverse proxy sits in front of backend servers, accepting client connections and forwarding requests to appropriate backends. Unlike a forward proxy (client-side), a reverse proxy is server-side and invisible to clients. Provides TLS termination, caching, compression, rate limiting, and security filtering. Nginx, Caddy, and Envoy are common reverse proxies.