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IPv4

IPv4 is the 32-bit addressing system most of the internet still runs on, giving every device a number like 203.0.113.42. Its roughly 4.3 billion addresses ran out years ago, which is why clean IPv4 is scarce and expensive.

Last updated August 14, 2026

Definition

IPv4 (Internet Protocol version 4) is the addressing scheme most of the internet still runs on. It gives every connected device a 32-bit number, written as four values from 0 to 255 separated by dots — 203.0.113.42. Deployed in 1983, it was never designed to carry the traffic of an entire planet, and it does.

How an address is structured

An IPv4 address is not one number but two joined together: a network part saying which network you are on, and a host part saying which device you are within it. A prefix length after a slash marks the split.

  • /24 — the first 24 bits are the network, leaving 256 addresses. The common unit of a subnet, and the block size anti-bot systems most often ban as one.
  • /16 — 65,536 addresses.
  • /32 — a single address.

This has a commercial consequence. Proxy addresses are bought and blocked in blocks, so "1,000 IPs" spread across four /24s is a far weaker product than 1,000 spread across two hundred.

Public, private, and reserved ranges

  • 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16 — private ranges, usable inside any network but not routable on the internet. Your router's 192.168.1.1 is one of many millions.
  • 127.0.0.0/8 — loopback. 127.0.0.1 is always the machine you are on.
  • 100.64.0.0/10 — shared space for CGNAT, where carriers put customers who no longer get a public address of their own.

Running out, and what it cost

32 bits allows roughly 4.3 billion addresses, which sounded limitless in 1983. The regional registries exhausted their free pools between 2011 and 2019, and the workarounds shaped the internet we now use.

  • NAT lets a whole household share one public address behind a router.
  • CGNAT extends the same trick upwards, sharing one public address across many customers. It is standard on mobile networks, and it is exactly why mobile proxies are so hard to block — banning one address would cut off thousands of real subscribers.
  • A resale market emerged, with IPv4 blocks trading as genuine assets. Scarcity, not technology, is why clean IPv4 costs what it does.

IPv4 vs IPv6 at a glance

  • Size — 32-bit, about 4.3 billion addresses, against IPv6's 128-bit and effectively unlimited supply.
  • Notation — four decimal numbers with dots, against eight hexadecimal groups with colons.
  • Sharing — IPv4 depends on NAT because it must; IPv6 gives every device its own public address.
  • Support — every site on the internet answers over IPv4. A significant minority still do not answer over IPv6.
  • Cost — IPv4 is scarce and priced accordingly; IPv6 is abundant and close to free.

Why proxies are almost always IPv4

Compatibility settles it. A proxy is only useful if it can reach the target, and every target is reachable over IPv4 while many still are not over IPv6. Anti-bot systems, geolocation databases, and reputation scoring are also far more mature for IPv4 — which cuts both ways, since your address is judged more accurately but a clean one is worth more. Residential, datacenter, and ISP pools are all sold as IPv4 for this reason, and will be for years yet.

Examples

1

192.168.1.1 — the private address of a typical home router

2

8.8.8.8 — Google's public DNS resolver, short by design so people remember it

3

127.0.0.1 — loopback, always the machine you are sitting at

4

203.0.113.0/24 — a 256-address block, the unit proxies are bought and banned in

5

100.64.0.0/10 — the shared range carriers use for CGNAT customers

Common Use Cases

Addressing and routing devices across the public internet
Buying residential, ISP, or datacenter proxies, which are sold as IPv4
Sharing one public address across a whole household through NAT
Geolocating a visitor from their IP address
Allowlisting a fixed address for API or server access
Judging proxy pool quality by counting distinct /24 subnets rather than addresses

Frequently Asked Questions

About 4.3 billion, since the format uses 32 bits. A large share of those are reserved for private, loopback, and special-purpose use, so the routable public pool is smaller still — and it has been fully allocated for years.
It says how many leading bits identify the network. A /24 fixes the first three numbers and leaves 256 addresses. It matters practically because blocklists usually operate on whole ranges, so one flagged address can drag its neighbours down with it.
Because every website answers over IPv4 and a meaningful share still do not answer over IPv6. Add better geolocation and reputation data, and IPv4 remains the only choice that reliably reaches the targets people actually want to reach.
Public addresses are globally unique and routable on the internet. Private ranges like 192.168.x.x work only inside a local network and are reused by millions of homes simultaneously, which is why your router's address looks identical to everyone else's.
Yes. Every regional registry exhausted its free pool between 2011 and 2019. Addresses still change hands, but only through leasing and resale, which is what turned IPv4 from a free resource into a traded asset with a market price.
Network Address Translation lets many devices behind one router share a single public address, with the router tracking which internal device each connection belongs to. Without it, IPv4 would have run out completely decades ago.
Not soon. Too much of the internet depends on it, and dual-stack networks let both protocols run side by side indefinitely. Expect IPv4 to stay the common denominator — and stay expensive — for a long time yet.

Keep Learning

All terms

Residential Proxy

A residential proxy routes your traffic through a real home internet connection, so websites see an ordinary ISP customer rather than a server in a data centre.

Read definition

Datacenter Proxy

A datacenter proxy is an IP address belonging to a hosting company rather than an internet provider. It is fast, cheap and available in bulk — and instantly identifiable to any site that checks who owns the address.

Read definition

CGNAT (Carrier-Grade NAT)

CGNAT is a technique carriers use to share one public IP among many customers — which is exactly why mobile proxy IPs are so trusted and hard to block.

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Subnet

A subnet is a smaller network carved out of a larger IP address range, grouping related addresses together. It helps organize and route traffic efficiently.

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IPv6

IPv6 is the 128-bit successor to IPv4, built to end the address shortage rather than work around it. Addresses are effectively unlimited and nearly free — but only useful against targets that actually support it.

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ASN (Autonomous System Number)

An ASN identifies a network on the internet — a block of IP addresses run by one organisation. It reveals whether an IP belongs to a home ISP, a data centre, or a mobile carrier.

Read definition
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