Proxy Server

A proxy server sits between two parties in a network conversation and relays traffic between them. Instead of connecting directly to a website, a client sends its request to the proxy, which makes the request itself and passes the response back. Because all traffic flows through it, the proxy can log, filter, cache, or modify requests and responses.

The key distinction is whose side the proxy is on. A forward proxy works for clients: it sits in front of a group of users, such as a company network, and sends their requests out to the internet, so websites see the proxy's IP address rather than each user's. A reverse proxy works for servers: it sits in front of one or more backend servers, receives requests from the internet, and forwards them inside, often handling TLS, caching, compression, and load balancing so clients never talk to the backends directly.

Think of a forward proxy as a personal assistant who places calls on your behalf, and a reverse proxy as a company switchboard that answers every incoming call and routes it to the right department. Organizations use forward proxies to enforce browsing policies, cache common downloads, and log outbound traffic, and developers often configure one through the HTTP_PROXY and HTTPS_PROXY environment variables. Load balancers, API gateways, and CDNs are all built on the reverse proxy idea.

A proxy is often confused with a VPN. A typical proxy handles traffic for specific applications or protocols, such as a browser's HTTP requests, and doesn't necessarily encrypt it, while a VPN routes all of a device's traffic through an encrypted tunnel. For HTTPS, a forward proxy usually just opens a tunnel with the HTTP CONNECT method and can't read the encrypted content, unless it is set up to intercept TLS with its own trusted certificate.