Glossary
The proxy glossary, without the fluff.
121 terms from across proxies, networking and web scraping, each defined in plain language and, where it matters, with the real-world detail that decides how the thing actually behaves. No dictionary glosses.
Start here: type is four questions, not one
Most confusion about proxies comes from treating one word as one decision. Whose network the address belongs to, whether that address changes, who else is using it, and which protocol you speak to it are four independent questions, and every real product answers all four at once. If a page here seems to contradict another, it is usually because the two are answering different ones.
If you want the whole picture in one read before diving into definitions, the guide to every proxy type walks through all four and ends with how to choose.
Proxy types
The families a proxy can belong to, and the axes people confuse for each other. Whose network owns the address is one question, whether it changes is a second, and who else is on it is a third. Every real product answers all three, and a provider naming only one has left the other two unstated.
Anonymous proxy
A proxy that hides your real IP address but still identifies itself as a proxy to the sites you visit.
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Bandwidth sharing
The supply side of residential proxies: apps and SDKs through which ordinary people lend their home connection as an exit, for compensation or without knowing.
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Caching proxy
A forward proxy that stores copies of responses and serves them again, built for saving bandwidth rather than for anonymity.
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Datacenter proxy
A proxy whose IP address is hosted in a commercial data center rather than assigned to a home, making it fast and cheap but easy for sites to identify as non-residential.
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Dedicated proxy
A proxy IP address assigned to a single customer, so its reputation reflects only your own traffic.
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Distorting proxy
An anonymity grade that hides your real IP but deliberately sends a false one in its place, sitting between an anonymous and a transparent proxy.
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DNS proxy
A service that intervenes at the name-lookup stage rather than carrying your traffic, covering everything from router DNS forwarding to smart DNS unblocking.
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Elite proxy
A proxy that hides your real IP and forwards no header admitting a proxy is in the path, so the request reaches the site shaped like a direct connection.
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Gateway proxy
A single entry point that routes your traffic into a whole pool of exit IPs, so you connect to one address and reach many.
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HTTP proxy
A proxy that understands the HTTP protocol and forwards web requests, optionally reading and modifying headers along the way.
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ISP proxy
A proxy hosted in a data center but registered to a consumer ISP, combining datacenter speed and stability with the trust of a residential network.
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Mobile proxy
A proxy that routes traffic through an IP address assigned by a mobile carrier to a phone or cellular modem, carrying the strongest trust of any proxy type.
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Open proxy
A proxy that accepts connections from anyone with no authentication, which is what almost every address on a free proxy list actually is.
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Peer-to-peer proxy
A residential network whose exits are other users' devices rather than managed servers, which is how most residential pools are actually built.
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Proxy pool
The full set of IP addresses a provider can route you through, and the number behind a rotating proxy.
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Residential proxy
A proxy that routes your traffic through an IP address assigned by an internet service provider to a home connection, so requests look like an ordinary person browsing.
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Rotating proxy
A proxy setup that assigns a different IP address to each request or on a timer, spreading traffic across a pool so no single address draws attention.
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Semi-dedicated proxy
A middle tier where an address is shared among a small, fixed number of users rather than one person or an unbounded crowd.
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Shared proxy
A proxy whose IP address is used by more than one customer at the same time, cheaper than a dedicated address but with reputation you do not fully control.
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Sneaker proxy
Proxies marketed for limited-release sneaker and streetwear drops, where the real requirement is many trusted addresses ready in a narrow window.
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SOCKS5 proxy
A proxy speaking the SOCKS5 protocol, which forwards any kind of TCP or UDP traffic without inspecting it, not just web requests.
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Static proxy
A proxy that keeps the same IP address for your exclusive use over an extended period, rather than rotating it between requests.
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Transparent proxy
A proxy that passes your real IP address through and often intercepts traffic without you configuring it, common in networks, useless for anonymity.
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Virgin proxy
A marketing label for a proxy IP sold as never previously used, a claim that is part verifiable freshness and part unverifiable history.
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Networking
The plumbing underneath everything else. What an address actually is, why there are not enough of them, how blocks and networks carry reputation as a unit, and where the lookups happen. Most surprises with proxies turn out to be one of these facts arriving unannounced.
ASN
An autonomous system number identifies the network that owns a block of IP addresses, and it is how sites tell a home connection from a data center.
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CDN
A content delivery network, the geographically distributed cache layer that serves most large websites and decides at its edge how to treat your request.
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CGNAT
Carrier-grade NAT, the technique of putting many subscribers behind one shared public IP address to conserve scarce IPv4 space.
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DNS
The domain name system translates human-readable hostnames into IP addresses, and where that lookup happens can quietly expose your real location.
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DNS leak
When your DNS queries bypass the proxy and reveal your real network or location despite your visible IP being masked.
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Exit node
The last hop in a proxy chain, the address the destination site actually sees, as opposed to the gateway you connect to.
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Firewall
A barrier that allows or blocks traffic by rules, which is what stops a proxy on an unusual port from being reachable on a restrictive network.
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Forward proxy
A proxy that sits in front of the client and forwards its outbound requests, the ordinary sense of the word proxy, as opposed to a reverse proxy that fronts a server.
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Internet service provider
The company that connects a home or business to the internet and assigns the IP address whose ownership every site checks before trusting a request.
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IP address
The numeric label that identifies a device on a network and is the address a proxy substitutes for your own.
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IP geolocation
The inference of physical location from an IP address, reliable at country level and frequently wrong at city level, and the mechanism proxy geo-targeting relies on.
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IPv4
The original internet addressing scheme, with about 4.3 billion possible addresses, now so scarce that providers ration and share them.
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IPv6
The newer addressing scheme with a practically unlimited supply of addresses, adopted unevenly across the world's networks.
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Load balancer
Infrastructure that spreads incoming requests across many backend servers, a form of reverse proxy you meet from the outside when scraping.
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NAT
Network address translation, the technique that lets many devices share one public IP address by rewriting traffic as it passes through a router.
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Port
A numbered channel on an IP address that directs traffic to a specific service, such as the port your proxy listens on.
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Port forwarding
A rule that lets outside traffic reach a specific device behind NAT, and the reason some proxies can accept inbound connections and others cannot.
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Proxy chaining
Routing traffic through more than one proxy in sequence, so each hop only knows its neighbours, not the whole path.
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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.
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Reverse DNS
The lookup that turns an IP address back into a hostname, often the most telling single fact about who operates an address.
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Subnet
A contiguous block of IP addresses managed as a unit, often shared reputation and all.
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TCP
The connection-oriented protocol that carries almost all proxy traffic, providing ordered, reliable delivery at the cost of a setup handshake.
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Tor
The volunteer-run anonymity network that routes traffic through three encrypted hops, built for privacy rather than for the work proxies are bought for.
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UDP
The connectionless transport protocol behind DNS, QUIC and real-time traffic, which most proxies cannot carry and SOCKS5 optionally can.
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VPN
A virtual private network that encrypts and routes all of your device's traffic through one server, where a proxy usually routes a single app.
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WebRTC leak
When a browser's real-time communication feature exposes your true IP address even though your traffic runs through a proxy.
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WHOIS
The public registration record system that says who holds an IP address or domain, and the raw source behind every ownership lookup in this glossary.
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Protocols & authentication
How your client and the proxy talk to each other, and what that conversation reveals. This is where the anonymity grades live, because only a protocol that understands your request can add a header describing it.
Cookie
A small piece of state a site stores in your client and reads back on every request, the mechanism behind logins, consent banners and a lot of bot scoring.
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HTTP CONNECT
The HTTP method that turns a proxy into a blind tunnel, which is how an HTTP proxy carries HTTPS traffic it cannot read.
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HTTP header
The name-and-value lines sent with every web request and response, where a client describes itself and where proxies leave or remove their traces.
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IP whitelisting
Authorising a proxy by pre-approving the IP addresses allowed to use it, instead of sending a username and password.
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PAC file
A proxy auto-config file: one JavaScript function that decides, per request, whether traffic goes direct or through which proxy.
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Proxy authentication
How a proxy verifies you are allowed to use it, most commonly by username and password or by allowing specific source IPs.
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QUIC
The transport behind HTTP/3, built on UDP to fix TCP's delays, and the reason a proxied browser quietly falls back to older protocols.
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Reverse proxy
A proxy that sits in front of servers rather than clients, handling incoming requests on their behalf, the opposite direction from the forward proxies used for scraping.
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SNI
The field in a TLS handshake that names which site you are connecting to, sent in the clear and readable by anyone on the path including a proxy.
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SOCKS4 proxy
An older version of the SOCKS protocol that relays TCP traffic but lacks authentication, UDP support and remote DNS.
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Sticky session
A rotating-proxy feature that keeps you on the same exit IP for a set duration so a multi-step task can complete without the address changing underneath it.
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TLS / SSL
The encryption that protects HTTPS traffic, which a proxy tunnels through untouched rather than reading.
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WebSocket
A protocol that upgrades an HTTP request into a persistent two-way connection, used for live data feeds, and a special case for proxies to carry.
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WPAD
Web Proxy Auto-Discovery, the mechanism behind the automatically detect settings checkbox, which lets a network hand your machine its proxy configuration.
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Scraping & automation
The working vocabulary of collecting data at scale: what limits you, what identifies you, and what the defences are actually measuring. Almost none of it is about the address.
Antidetect browser
A browser built to run many isolated profiles, each with its own consistent fingerprint, cookies and proxy, so one machine can operate several plausible identities.
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API scraping
Collecting data by calling the JSON endpoints a page uses instead of parsing its HTML, usually the fastest, cheapest and most reliable route when one exists.
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Browser fingerprinting
Identifying a visitor from the combination of subtle browser and device traits, a layer of detection that survives changing your IP.
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CAPTCHA
A challenge designed to tell humans from bots, triggered far more often by suspicious network reputation than by any single request.
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CAPTCHA solver
A service that returns an answer to a challenge, either by human workers or by automation, treating the symptom of a low trust score rather than the cause.
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CSS selector
The pattern syntax invented for styling pages, borrowed by scrapers as the everyday way to select the elements worth extracting.
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Data parsing
Turning a fetched response into structured data, the half of scraping that happens after the network and breaks for entirely different reasons.
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Geo-blocking
Restricting or changing what a site shows based on the visitor's inferred country, which a proxy in the target country is meant to bypass.
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Geo-targeting
Deliberately choosing a proxy in a specific country, region or city so your traffic originates exactly where you need it to.
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Headless browser
A real browser running without a visible window, used to render JavaScript-heavy pages in automation.
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IP rotation
The practice of cycling through many IP addresses across a workload so no single one accumulates a suspicious request count.
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JavaScript rendering
The process by which pages build their content in the browser after loading, which decides whether fetching the HTML gets you data or an empty shell.
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Pagination
How a site splits a long list across many pages or loads, and the part of a scrape most likely to silently miss data or trap a crawler.
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Rate limiting
A site's cap on how many requests one source may make in a window, the most common obstacle a scraper meets.
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Retry logic
How a scraper handles failed requests, which done badly wastes bandwidth and escalates blocks, and done well quietly rescues most transient failures.
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robots.txt
A file at a site's root that tells crawlers which paths it prefers they avoid, a convention, not an enforced barrier.
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Scraper API
A service that takes a target URL and returns the page data, handling proxies, rendering, retries and anti-bot friction behind a single endpoint.
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SERP
A search engine results page, the most location-sensitive and most defended page type on the web, and the raw material of the SEO industry.
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User agent
The string a client sends to identify its browser and operating system, one of the simplest signals a site checks against your IP.
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Virtual browser
A browser that runs on remote infrastructure and is driven over the network, rented by the session instead of run on your own machines.
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Web crawler
A program that follows links from page to page to discover and fetch content, the traversal engine underneath large-scale scraping.
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Web scraping
The automated collection of data from websites, the single most common reason people use proxies at scale.
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XPath
A query language for addressing parts of an HTML or XML document, the more powerful of the two ways scrapers point at the data inside a page.
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Detection & reputation
How a site decides whether to trust you. Detection is a score assembled from many weak signals rather than a yes or no, which is why the same setup passes on Monday and is challenged on Thursday.
Akamai Bot Manager
The enterprise bot-defence built into Akamai's CDN, known for the telemetry its client-side script gathers and the tracking cookie it issues.
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Anti-bot system
A layered defence, network, fingerprint and behaviour checks combined, that sites use to separate automation from real users.
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Behavioral analysis
Detection that scores how you interact rather than what you send, catching automation through timing, movement and navigation a clean address cannot fix.
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Botnet
A network of compromised devices controlled without their owners' knowledge, the criminal end of where proxy and residential supply can come from.
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Canvas fingerprinting
A fingerprinting technique that has your browser draw an image and reads back the tiny hardware-specific differences in how it rendered.
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Clean IP
An address that carries no negative record a site can look up: off every blocklist, no abuse history, owned by a consumer ISP, and rated low risk by a fraud engine.
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Cloudflare
A CDN and security layer that fronts a large share of the web and includes some of the most common anti-bot challenges scrapers meet.
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Cloudflare Turnstile
Cloudflare's own CAPTCHA replacement, which verifies visitors through background browser checks instead of puzzles and usually shows only a checkbox or nothing.
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DataDome
A real-time bot-protection service that scores every request in milliseconds from device, network and behavioural signals, common on e-commerce and classifieds.
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Device fingerprint
The identity built from a device's hardware and system traits, more stable than a browser fingerprint and harder to change because it reflects the physical machine.
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Fraud score
A single number that fraud-detection services assign to an IP address to summarise how risky traffic from it looks.
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FunCaptcha (Arkose Labs)
A challenge system from Arkose Labs built around rotating interactive puzzles, designed to impose cost on attackers rather than just to sort humans from bots.
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hCaptcha
A privacy-positioned CAPTCHA that pays the sites deploying it, best known as Cloudflare's former default and for its image-classification challenges.
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Honeypot
A trap planted for automation, a link or field invisible to humans, that flags anything which interacts with it as a bot.
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Imperva (Incapsula)
A long-established enterprise security platform combining a CDN, a web application firewall and bot management, formerly branded Incapsula.
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IP blacklist
A published list of IP addresses flagged for abuse, which sites and mail servers consult to refuse traffic outright.
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IP reputation
The accumulated trust score a site or third-party service assigns to an IP address based on its network, history and behaviour.
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Kasada
An aggressive bot defence that makes clients solve a hidden computational challenge and actively frustrates automation rather than merely blocking it.
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PerimeterX (HUMAN)
A behavioural bot defence, now part of HUMAN Security, that leans on a client-side sensor and code-integrity checks rather than on network reputation alone.
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Port scanning
Probing an address across many ports to find services that answer, which is how most public proxy lists are assembled in the first place.
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Proxy detection
The set of techniques sites use to decide whether a visitor is behind a proxy, ranging from network lookups to behavioural analysis.
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reCAPTCHA
Google's challenge system, now mostly an invisible score from 0.0 to 1.0 rather than a puzzle, drawing on the signals a Google-scale presence can see.
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TLS fingerprint
An identifier built from how a client negotiates encryption, used to spot automation even through a clean IP.
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Web application firewall
A filter that inspects incoming web requests against rules and blocks the ones that look malicious, a different layer from the bot management scrapers usually mean.
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X-Forwarded-For
An HTTP header a proxy can add to name the original client's IP, and the single biggest tell that separates an anonymous proxy from a transparent one.
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Performance
What you are buying and how to tell whether you got it. Uptime, latency, bandwidth and success rate measure different things, and the one quoted loudest is rarely the one that decides whether your job finishes.
Bandwidth
The volume of data a proxy can move, and the unit residential and mobile proxies are typically billed by.
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Concurrency
How many requests you run at the same time, the main lever on scraping throughput and a common hidden limit.
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Latency
The delay between sending a request through a proxy and getting a response, driven largely by physical distance to the exit.
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Packet loss
When data packets fail to arrive and must be resent, a quiet cause of slow, unreliable proxy connections that latency alone does not reveal.
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QPS
Queries per second, the rate at which you send requests, which has to be balanced against both a target's limits and a proxy's concurrency ceiling.
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Success rate
The share of requests that come back with the data you wanted, the metric that actually measures a proxy's worth.
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Time to first byte
The delay between sending a request and the first byte of the response arriving, the performance number that isolates the proxy path from download size.
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Uptime
The share of time a proxy is actually reachable and working, which for residential pools is a live measurement rather than a guarantee.
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