IPv4 vs IPv6

IPv4 and IPv6 are the two addressing systems in use on the internet: IPv4 addresses are 32 bits long and written like 203.0.113.5, while IPv6 addresses are 128 bits long and written like 2001:db8::1. Both carry the same traffic; the difference that matters commercially is how many of each exist.

Scarcity is the whole story

IPv4 tops out at about 4.3 billion addresses and they ran out years ago, which is why they are leased, traded, and why carriers hide whole cities behind CGNAT. IPv6 has room for an unimaginable number, so a provider can hand out enormous blocks at almost no cost.

Why it matters when you buy proxies

When you see proxies advertised at a price that seems impossible, check which family they are. Cheap IPv6 is cheap because the addresses cost the seller nothing — and the same abundance makes them easy for a site to discount, since one customer can hold millions of them and a subnet ban on a whole IPv6 block costs the site nothing either. Plenty of target sites still do not accept IPv6 connections at all, in which case the proxy simply will not work.

A concrete example

A listing offering ten million IPv6 addresses for a few dollars and one offering a single IPv4 mobile address for a monthly fee are not competing products. The first is a large number of interchangeable addresses; the second is one scarce address a site has to treat as it treats a real subscriber's.