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How IP addresses, DNS, proxies and VPNs actually work, explained from the standards. To test your own connection, use the free tools.

Networking basics

What is an IP address? IPv4, IPv6, public and private
An IP address identifies a device's network interface so packets can reach it. IPv4 vs IPv6, public vs private, and what your address reveals.
What is DNS? How a site name becomes an IP address
The Domain Name System is a distributed database that turns site names into IP addresses. The lookup steps, the record types, and who sees your queries.
What is an ASN? Autonomous systems and internet routing
An ASN identifies an autonomous system, a network with one routing policy that announces its addresses over BGP. What it reveals about an IP.
What is CGNAT? Why mobile users share one IP address
CGNAT is address translation inside the provider's network: many subscribers leave from one public IPv4 address, told apart by port. How it works.
How IP geolocation works, and why it is often wrong
An IP address carries no location. Databases estimate it from registry records, operator feeds and latency. Where the data comes from and why it errs.

What is a proxy server and how does it work?
A proxy is an intermediary server that sends your requests to websites and relays the replies, so sites see its IP instead of yours.
SOCKS5 vs HTTP proxy: what is the difference?
An HTTP proxy understands web requests and can read them; SOCKS5 relays any connection without parsing it. How each works and when to use which.
What is HTTP CONNECT and how does an HTTPS proxy work?
CONNECT asks a proxy to open a TCP tunnel to a site and relay bytes unchanged. An HTTPS proxy also encrypts the path between you and the proxy.
Forward proxy vs reverse proxy: what is the difference?
A forward proxy is chosen by users and represents them to websites; a reverse proxy sits in front of a site's servers and represents them to visitors.
How proxy authentication works: passwords and IP allowlists
Proxy authentication proves you may use a proxy, with a username and password or an allowlist of IP addresses. How each method works and what protects it.

Proxy quality: what decides it and how to measure it
Proxy quality is a set of measurable factors: address type and reputation, success rate, latency, session stability, leak protection and encryption.
Residential vs data center vs mobile proxies
How residential, data center and mobile proxies differ: who owns the address, how many people share it, how sites classify it, and when to use each.
Rotating vs sticky proxies: when to use each
A rotating proxy changes the exit address per connection or interval; a sticky one keeps it for a session. How each works, when to use it, how to test it.
What is IP reputation and how do you check it?
IP reputation is a judgement blocklists and scoring services form from an address's behaviour and network, used to accept, challenge or refuse requests.
Proxy speed: latency, throughput and TTFB explained
Proxy speed is three measures: latency, throughput and time to first byte. What drives each one, and how to measure them with curl -w timings.

What is a VPN and how does it work?
A VPN is an encrypted tunnel between your device and a server that carries your traffic to the internet. What happens to each packet, and who sees what.
How WireGuard works: keys, handshake and AllowedIPs
WireGuard is a UDP tunnel with a one round trip handshake and short public keys. The handshake, AllowedIPs, and how it compares with IPsec and OpenVPN.
What is split tunneling and when should you use it?
Split tunneling sends part of your traffic through a VPN and the rest over your normal connection. How paths are chosen, the risks, and how to test it.
What is geo-blocking and why do services use it?
Geo-blocking is when a service limits what it offers by the country it thinks you are in, usually from your IP. How it knows, where it blocks, and why.
How do websites detect a VPN or proxy?
Sites do not see the word VPN in your traffic. They compare signals: who owns the address, its history, whether DNS, WebRTC and time zone agree, latency.

What is a DNS leak and how do you detect one?
A DNS leak is when your device sends domain name lookups outside the VPN or proxy, usually to your ISP. Why it happens, how to test, how to stop it.
What is a WebRTC leak and how do you stop it?
A WebRTC leak is when the browser's real-time feature exposes your real IP to any page, even behind a proxy. How it works, how to test, how to stop it.
What is an IPv6 leak and why does it happen with a VPN?
An IPv6 leak happens when a tunnel carries only IPv4, so IPv6 traffic leaves directly with your real address. Why it happens, how to test, how to stop it.
What is a VPN kill switch and how does it work?
A kill switch blocks all traffic outside the VPN tunnel when it fails, so the device cannot fall back to your real address. How it works, how to test it.
What is DNS over HTTPS (DoH)? How it differs from DoT
DoH sends DNS lookups inside an encrypted HTTPS connection, so the network in between cannot read them. How it works and how it compares to DoT.