Proxy server (network intermediary)

How a proxy works

At a basic level a client opens a connection to the proxy and asks it to fetch a resource on its behalf. The proxy then makes the corresponding connection to the destination server, receives the response, and returns it to the client. Because the proxy intermediates the interaction, it can log activity, enforce policies, rewrite requests, or store copies of responses to answer future requests without contacting the upstream server (caching). Proxies may operate at different layers of the networking stack and support protocols such as HTTP/HTTPS, SOCKS, or FTP.

Common types and roles

• Forward proxy: Sits between clients and external servers; often used to provide anonymity, content filtering, or caching for internal users.
• Reverse proxy: Placed in front of one or more servers to distribute load, terminate TLS, cache content, and protect origin servers.
• Transparent proxy: Intercepts traffic without requiring client configuration, typically for caching or monitoring.
• Tunneling or gateway proxy: Forwards data without modifying it, and can create encrypted tunnels (for example using SSL/TLS) between endpoints.
• SOCKS and application-layer proxies: Offer general-purpose TCP/UDP relaying or protocol-specific handling (such as HTTP proxies for web traffic).

Features and practical uses

Proxies provide several practical benefits: caching reduces latency and external bandwidth use; access controls and authentication restrict who can reach particular resources; content inspection enables malware scanning and policy enforcement; and anonymization can hide client addresses for privacy. In server deployments, reverse proxies support load balancing, health checks and TLS termination, often improving scalability and resilience. Organizations also use proxies for parental controls, workplace content filtering and compliance logging.

History and evolution

Proxy technology emerged alongside early packet- and request-based networks and became widespread with the growth of the World Wide Web, when caching and filtering reduced network costs and improved perceived performance. Over time proxies have evolved to handle encrypted protocols, integrate with identity systems, and operate at larger scale as software-defined or cloud-hosted services. Modern deployments must balance functionality with privacy, security and legal considerations.

Distinctions and notable facts

Proxies differ from virtual private networks (VPNs) in scope and mechanism: VPNs typically create an encrypted tunnel carrying all network traffic between endpoints, while proxies selectively handle specific protocols or connections. A proxy may be configured on the client, on a gateway device, or as a middlebox somewhere in the path between client and server. Because proxies can modify or log traffic, administrators must consider trust and encryption: for example, a proxy that terminates TLS can inspect content but must be explicitly trusted by clients. For more detailed technical references see resources for network administrators.