What is a Proxy?

What a proxy server is

A proxy server is a machine that makes requests on your behalf. Instead of your device connecting directly to a website, it connects to the proxy, the proxy connects to the website, and the response comes back the same way. The website sees the proxy's IP address and network, not yours. The word comes from the Latin procurare, "to act for another" — which is exactly the job.

Think of it as a mailroom. You hand outgoing mail to the mailroom; it sends everything from its own address and sorts the replies back to you. Anyone watching the recipient's end sees the mailroom, not your desk.

How a forward proxy handles a request

For plain HTTP, your client sends the full URL to the proxy, which fetches it and can inspect, cache, filter, or log the content. For HTTPS, the client sends an HTTP CONNECT to the proxy, which opens a raw TCP tunnel to the destination; the TLS handshake then happens end-to-end, so the proxy sees the destination host and byte counts but not the decrypted content (unless the network installs its own root certificate for interception). SOCKS5 proxies work one layer lower and can carry any TCP or UDP traffic, not just web.

Types of proxy

• Forward proxy — sits in front of clients. Used for content filtering, caching, access logging, and presenting a single egress IP for an organisation.
• Reverse proxy — sits in front of servers. Terminates TLS, load-balances, caches, and shields origin servers (nginx and HAProxy in this role). Users don't configure it; the site operator does.
• Transparent proxy — intercepts traffic at the network with no client configuration. Common on corporate and public Wi-Fi for filtering; the user may not know it's there.
• Anonymous / elite proxy — a forward proxy that omits headers like Via and X-Forwarded-For so the destination can't easily tell a proxy is in use.
• Residential vs. datacentre proxy — residential proxies route through real ISP-assigned IPs and are harder to block; datacentre proxies are cheaper and faster but easily identified as hosting ranges.

Proxy vs. VPN

A proxy usually redirects a single application's traffic (your browser) and often doesn't encrypt the link between you and the proxy. A VPN captures all traffic from the device at the OS level and encrypts the tunnel end to end. Use a proxy for lightweight, per-app IP changes or caching; use a VPN when you need encryption and whole-device coverage on an untrusted network.

What proxies are good for — and not

• Good for: hiding your origin IP from a destination, caching to save bandwidth, enforcing an acceptable-use policy, accessing geo-restricted content, and consolidating outbound traffic behind one address for allow-listing.
• Not a privacy cure: a free public proxy operator can log everything and, with HTTP, read and modify unencrypted pages. Prefer HTTPS end to end, and don't send credentials through a proxy you don't control.

Many private and corporate proxies require an authenticated login before they route traffic. If you run one, protect that account with a unique strong password rather than one you've used elsewhere.

Common software

Proxy servers: Squid (caching/forward), nginx and HAProxy (reverse), Apache Traffic Server, Varnish (HTTP cache), 3proxy and Dante (SOCKS).
Client-side tools: FoxyProxy and SwitchyOmega (browser profile switching), Proxifier (force desktop apps through a proxy), Shadowsocks and Psiphon (censorship circumvention).