Proxy server
A server that sits between you and the internet, making requests on your behalf so the destination sees the server's address instead of yours.
A proxy server is a machine that makes requests on your behalf. Rather than connecting to a website yourself, you connect to the proxy, it opens the connection to the destination, and it relays the response back to you. The destination sees the proxy's address and has no visibility of yours, which is the entire mechanism and the reason everything else exists.
That single indirection buys three quite different things depending on why it was set up. Anonymity, because your real address never reaches the destination. Access, because the request now originates wherever the proxy sits, which is what makes geography selectable. And control, because an organisation placing a proxy in front of its own network can filter, cache or log everything that passes through. Identical mechanism, three unrelated motives.
The direction it faces is what separates the two families, and confusing them causes more misunderstanding than any other term here. A forward proxy works for the CLIENT: you configure it, and it hides you from the servers you visit. A reverse proxy works for the SERVER: the site's operator puts it in front of their own infrastructure, and it hides their machines from you while handling caching, load balancing and TLS. When someone says proxy without qualification in a buying context, they mean the first.
Everything else in this glossary is a way of describing what KIND of proxy server you are talking to. Residential or datacenter describes whose network the address belongs to. HTTP or SOCKS5 describes the protocol you speak to it. Rotating or static describes whether the exit changes. Shared or dedicated describes who else is using it. The server in the middle is the constant; those four axes are the variables, and they combine independently.
Worth being clear about what it does not do, because this is where expectations break. A proxy substitutes an address. It does not encrypt your traffic unless the traffic was already encrypted, it does not hide you from the proxy operator, who sees everything not protected by TLS, and it does nothing about the identity your browser and TLS handshake broadcast above the network layer. It is one substitution, executed well, and treating it as a cloak leads to the disappointment described throughout the rest of these entries.
Frequently asked questions
What is the difference between a proxy server and a VPN?
Scope and encryption. A VPN operates at the operating system level, so every connection the whole device makes travels through one encrypted tunnel to one exit. A proxy is usually configured inside a single application and routes only that, and does not necessarily encrypt anything itself. The proxy model wins when you need many different addresses or per-application control; the VPN model wins when you want everything on the device covered at once.
Does a proxy server encrypt my traffic?
Not by itself. It relays what you send, so HTTPS traffic stays encrypted because it already was, and plain HTTP traffic stays readable because it always was. The proxy operator can see any unencrypted content and, even with HTTPS, sees which hostnames you reached and when. If encryption is the goal, that comes from the protocol you use, not from adding an intermediary.
Is a proxy server the same as a reverse proxy?
No, and the difference is which side it serves. A forward proxy, which is what people mean in a buying context, is configured by you and hides you from the sites you visit. A reverse proxy is installed by a site's operator in front of their own servers, handling caching, load balancing and TLS, and hides their infrastructure from you. Same word, opposite direction, entirely different purpose.
How do I set up a proxy server?
For a proxy you have bought, you configure the host, port, username and password in whichever client will use it: a browser setting, an environment variable, or a proxies argument in your HTTP library. Running your own is a different project involving software such as Squid or a SOCKS daemon on a machine you control, and it gets you one address you already had rather than a pool.
Back to the full glossary.