Proxy glossary

50 proxy terms, each answered in a sentence and then explained. Written for people choosing or setting up a proxy, not for network engineers.

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407 Proxy Authentication Required: A 407 error means the proxy did not accept your login. The username or password is wrong, was cut short, or was never sent at all.

Anonymous proxy: An anonymous proxy hides your IP address from the website. An elite proxy also hides the fact that a proxy is being used at all.
Antidetect browser: An antidetect browser runs many separate browser profiles, each with its own fingerprint, cookies and proxy, so they look like different people.
ASN: An ASN, or autonomous system number, identifies the network that owns a block of IP addresses, such as an internet provider or a hosting company.

Backconnect proxy: A backconnect proxy is a single gateway address that forwards your requests through a changing pool of IP addresses behind it.
Bot detection: Bot detection is the set of checks a website runs to tell people from programs: the IP address, the browser fingerprint and the behaviour.
Browser fingerprint: A browser fingerprint is the mix of details a browser reveals, such as screen size, fonts and graphics card, that together single it out.

Captcha: A captcha is a test a website shows to check that a visitor is a person, such as picking images or ticking a box, before letting them continue.
Captcha solver: A captcha solving service takes a captcha from your program, solves it with people or software, and returns the token the website asks for.
CGNAT: CGNAT, or carrier-grade NAT, is how a phone carrier puts hundreds of customers behind one public IP address at the same time.
Concurrent connections: Concurrent connections are the requests a program has open through a proxy at the same moment. More of them finish a job sooner.

Datacenter proxy: A datacenter proxy uses an IP address that belongs to a hosting company. It is fast and cheap, and the easiest kind for a website to recognise.
Dedicated and shared proxies: A dedicated proxy is an IP address only you use. A shared proxy, or a pool, is used by many customers, at different moments or at once.
DNS leak: A DNS leak is when a program looks up site names through your own network instead of through the proxy, revealing which sites you visit.

Exit IP: The exit IP is the address your request leaves the proxy network from. It is the address the website sees and logs as its visitor.

Forward and reverse proxy: A forward proxy stands in front of visitors and hides them from websites. A reverse proxy stands in front of a website and hides its servers.

Geo-blocking: Geo-blocking is when a website shows different content, or none at all, depending on the country your IP address is registered in.
Geo-targeting: Geo-targeting means choosing the country, state or city your proxy request leaves from, so a website shows what local visitors see there.

Headless browser: A headless browser is a real browser that runs without a window and is driven by a program, used to load pages that need JavaScript.
HTTP proxy: An HTTP proxy is a proxy that speaks the web's own protocol. Almost every program supports it, and it carries both http and https sites.
HTTPS through a proxy: Yes. An HTTP proxy opens https sites through a tunnel, using a request called CONNECT. The traffic inside stays encrypted end to end.

IP ban: An IP ban is when a website refuses requests from a particular IP address, usually after seeing too many requests or behaviour it disliked.
IP reputation: IP reputation is the trust a website places in an IP address, based on who owns it and how addresses like it have behaved before.
IP rotation: IP rotation means changing the IP address your requests come from, either on every connection or after a set time, to spread them out.
IP whitelisting: IP whitelisting lets a proxy accept requests from addresses you registered in advance, with no username or password in the request.
IPv4 and IPv6: IPv4 addresses are the older, short kind and are nearly used up. IPv6 addresses are longer and plentiful, which makes them much cheaper.
IPv6 proxy: An IPv6 proxy sends your requests out from an IPv6 address. It costs far less per gigabyte and works only on sites that support IPv6.
ISP proxy: An ISP proxy, also called a static residential proxy, is an address registered to a home internet provider but hosted on a server, so it never changes.

Mobile proxy: A mobile proxy sends your traffic through an IP address of a phone carrier, on a real 4G or 5G connection. Sites are slowest to block these.

Proxy and VPN: A VPN sends all of a device's traffic through one encrypted tunnel. A proxy is set per program and can use a different IP for each request.
Proxy authentication: Proxy authentication is how a proxy checks you are a paying customer: either a username and password, or a list of allowed IP addresses.
Proxy checker: A proxy checker is a tool that sends a test request through a proxy and reports whether it works, its exit IP address and its country.
Proxy format: A proxy format is the order in which a proxy's host, port, username and password are written on one line, which differs from tool to tool.
Proxy latency: Proxy latency is the extra time a request takes because it travels through a proxy before it reaches the website and comes back.
Proxy pool: A proxy pool is the whole set of IP addresses a proxy service can send your requests through. Each request is given one address from it.
Proxy port: A proxy port is the number after the host that tells your program which service to connect to: one port for HTTP and another for SOCKS5.
Proxy server: A proxy server is a computer that passes your requests on to a website, so the website sees the proxy's IP address and not yours.
Proxy traffic: Proxy traffic is the data that passes through a proxy, counted in gigabytes. Both what you send and what you download count toward it.

Rate limiting: Rate limiting is a cap on how many requests a website accepts from one visitor in a given time. Going over it brings errors or a block.
Residential proxy: A residential proxy sends your traffic through an IP address that belongs to a home internet connection, so websites see an ordinary household visitor.
Rotating proxy: A rotating proxy gives each new connection a different IP address from a pool, so no single address makes enough requests to be noticed.

Session ID: A session ID is a short label you add to a proxy username. Requests that carry the same label leave from the same IP address.
SOCKS5 proxy: A SOCKS5 proxy passes any kind of network connection, not only web pages, and can sign you in with a username and password.
Sticky session: A sticky session keeps the same proxy IP address for a set time, so several requests in a row look like they come from one visitor.
Subnet: A subnet is a block of neighbouring IP addresses that belong together. Websites often limit or block a whole block instead of one address.

TLS fingerprint: A TLS fingerprint is the pattern in how a program opens an encrypted connection. It reveals whether the visitor is a browser or a script.

Unlimited proxy: An unlimited proxy plan does not count traffic. You pay for a length of time and a speed, and use as much data as that speed carries.
User agent: A user agent is a line of text a browser or program sends with every request to say what it is, such as Chrome on Windows.

Web scraping: Web scraping is collecting information from web pages with a program instead of by hand, for example prices, listings or search results.
WebRTC leak: A WebRTC leak is when a browser's video-call feature reveals your real IP address to a website even though you are using a proxy.