Glossary

Anti-bot system

Software that decides whether a request came from a human, using signals well beyond the IP address.

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ASN

Autonomous System Number — the identifier of the network that owns an IP range, and a primary classification signal.

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Backconnect proxy

A single gateway address that transparently routes each request through a different address in the provider's pool.

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Buying guides

Bandwidth billing

Charging by gigabyte transferred — the standard model for residential proxies, and easy to underestimate.

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Browser fingerprinting

Building an identifier from browser and device characteristics exposed to JavaScript.

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CAPTCHA

A challenge intended to separate humans from automation, and usually a symptom rather than the problem itself.

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Carrier-grade NAT

Carrier-grade NAT is address translation performed inside an operator's own network, so that many subscribers share a single public address.

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Certificate pinning

Certificate pinning is the practice of accepting only a specific key or certificate for a host, rather than any certificate that chains to a…

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CIDR

CIDR is the notation and allocation scheme that writes a block of IP addresses as an address followed by a prefix length, such as…

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Concurrency

How many proxy connections you may run at once — often the real constraint on throughput, not bandwidth.

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Cookie jar

A cookie jar is the store a client keeps of the cookies it has received, keyed by domain and path, and replayed on later…

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Crawl budget

Crawl budget is the informal name for how much of a site a crawler will fetch in a given period.

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Datacenter proxy

A proxy hosted in a commercial datacentre. Fast and inexpensive, but easily identified as non-residential.

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DNS leak

A DNS leak is a name lookup that travels outside the path you intended, so a resolver you did not choose learns the hostname…

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Exit node

The final address in a proxy chain — the one the destination actually sees and records.

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Exponential backoff

Exponential backoff is a retry policy in which the wait between attempts grows by a constant factor each time, usually doubling.

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Forward proxy

A proxy that acts for the client. It sits between you and the internet and hides your address from destinations.

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Geo-targeting

Choosing where your proxy exits, from country level down to city or network in some services.

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Headless browser

A real browser engine driven programmatically with no visible window. Powerful, slow and expensive in bandwidth.

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Honeypot link

A honeypot link is a link placed on a page so that a person will never follow it, in order to identify clients that…

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HTTP CONNECT

The HTTP method that asks a proxy to open a raw tunnel, which is how HTTPS travels through an HTTP proxy.

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HTTP/2 fingerprint

An HTTP/2 fingerprint identifies a client from how it opens and drives the connection, rather than from the content of its headers.

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IP whitelisting

Authorising a proxy by the address you connect from, instead of sending a username and password.

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IPv6

IPv6 is the current version of the Internet Protocol, with addresses of 128 bits written as eight groups of four hexadecimal digits.

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ISP proxy

A datacentre-hosted address registered to a consumer ISP. Datacentre speed with residential registration, billed per IP.

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JA3 fingerprint

A JA3 fingerprint is a hash computed from selected fields of the TLS ClientHello, taken in the order the client sent them.

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Mobile proxy

A proxy exiting through a mobile carrier address, shared by many real handsets via carrier-grade NAT.

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Port

A port is a 16-bit number identifying one endpoint of a transport connection, so a single address can carry many independent conversations at once.

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Proxy authentication

How a proxy verifies who you are, and the meaning of the 407 status code defined in RFC 9110.

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Buying guides

Proxy pool

The set of addresses a provider can route your traffic through, and the source of every rotation decision.

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Proxy server

A server that makes requests on your behalf, so the destination sees the proxy's address instead of yours.

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Rate limiting

Capping how many requests a client may make in a period. The 429 status code is defined in RFC 6585.

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Referer header

Referer is a request header naming the resource from which the target URI was obtained.

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Residential proxy

A proxy whose exit address belongs to a consumer ISP, so the traffic appears to come from an ordinary home connection.

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Retry-After

Retry-After is a response header giving either a number of seconds to wait or an HTTP-date after which to retry.

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Reverse proxy

A proxy deployed in front of a server. Clients connect to it as if it were the origin, and it forwards to the real…

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robots.txt

A file telling crawlers which paths a site prefers they avoid. A convention, not an access control.

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Rotating proxy

A proxy endpoint that changes the exit address automatically, either on every request or on a timer.

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SOCKS5

A protocol that proxies any TCP or UDP traffic without inspecting it, defined in RFC 1928.

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Sticky session

A setting that keeps the same exit address for a fixed period, so a multi-step flow appears to come from one user.

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Subnet

A subnet is a contiguous block of addresses that share a common leading prefix and are administered as one network.

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Success rate

The share of requests that return a usable response. Meaningless without a sample size and a named target.

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TLS fingerprinting

Identifying a client from the structure of its TLS handshake, before any HTTP request is sent.

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TLS interception

TLS interception is the practice of terminating a client's encrypted connection at a middlebox that reads the plaintext and re-encrypts onward.

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Transparent proxy

In everyday use, a transparent proxy is one that intercepts traffic without any configuration on the client, so the client does not know it…

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User agent

The header a client uses to identify itself. Trivially changed, and therefore weak evidence on its own.

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Via header

Via is a standard HTTP header in which each intermediary records the protocol version it received the message on, together with a name for…

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Extracting structured data from web pages automatically. Lawful in many contexts and restricted in others.

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WebRTC leak

A WebRTC leak is the disclosure of a network address by the browser's real-time communication stack.

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