An IP address is a numerical label assigned to a device connected to a network, used to identify and locate that device so data can be routed to and from it correctly. Websites use the IP address of an incoming request to determine a visitor's approximate location and to apply access rules like rate limits or geo-restrictions.

Which IP address a request carries is the single signal proxies exist to change: a residential proxy substitutes an ISP-issued address, while a datacenter proxy substitutes one issued by a hosting provider, and the two look very different to a website evaluating the request.

IPv4 vs. IPv6

  • IPv4 (e.g., 192.168.1.1), offers about 4.3 billion unique addresses
  • IPv6, a newer format designed to accommodate the much larger number of internet-connected devices

In the proxy context, the IP address is the core resource being provided, a "proxy" is fundamentally an IP address (or pool of them) that requests are routed through. Everything about a proxy's usefulness, speed, trust level, geographic assignment, traces back to where and how its IP address was issued.