How many addresses can IPv6 hold?

The IPv6 standard (RFC4193) says A single implementation of an address family is to have at least 128 bits in the address. In practice the Internet Engineering Task Force (IETF) has decided on 65,535 addresses. However many of us see 64,000. The problem with using the worst case scenario of 64,000 addresses is that it is highly dependent on what you consider worst case scenario. For example, when I say that 1,000 users can get a single address you immediately think of an Internet Service Provider (ISP) where 1,000 users are allocated 64 bits of address space per user. However this assumes that all users have their own dedicated connection with no shared addressing. This is unlikely as even an internet cafe will have 10 - 20 users on a single DSL line at once. Each of those 10-20 users is allocated a 64-bit address. That would be 1024 users with 64-bit addresses.

If one of those users connects from a different DSL router there may be issues with routing. So 64-bit addresses may not be enough.

So how many addresses can the average user get? I looked up a report published in 2026 on IPv6 allocations in some countries around the world. In that report they give the number of unique hosts per network block. The blocks here refers to a single network or autonomous system boundary. Most ISPs and Governments run the IPv6 address pool as a ring so the data does not need to be aggregated by network.

Here is a chart showing the number of addresses per block by country: One can see why in 2026 when they published their report they assumed a lot of IPv6 traffic was being served off of a single prefix. This was probably correct since that time period IPv6 deployments in countries like China were just beginning to pick up.

The US is a strange case as they ran out of addresses before they passed the milestone of 32-bit addresses. The interesting thing is that their last 32 bit allocation was at 3.22.0/24. If I am counting these as a single block then that gives 4.0/30, which is the lowest possible size for a single block in IPv6.

Why did they not have enough addresses?

What is the address size of IPv6?

If I understood the document correctly, it is 128 bits.

So why not name 128-bit addressing scheme as IPv6?

Because IPv4 has been around for over 25 years, and most people still only know or think of it as being the standard protocol for internet traffic. If they were to call it IPv6 instead, then everyone would know that they are talking about a new protocol, and so would be less likely to try to use the address 128.0.2 (assuming the address is in one of those four billion of addresses) in their system.

The thing is, most networks will use both protocols. So on both the hosts themselves, and on routers, you'll often see both IP and IPv6 addresses next to each other. If the IP is an IP address that isn't valid for IPv6, it just looks like IPv4, but you know it's only there because you're using it on your network. If the IPv6 is some arbitrary weird address, then you have no idea what the hell you're doing.

So, really, why not call them both IPv4? Why not just call it Internet Traffic?

What is the subnet range of IPv6?

The IPv6 address space is represented by a collection of subnet prefixes.

Like IPv4's subnetting system, IPv6 subnetting is hierarchical and it uses a /64 as its basic unit. The IPv6 space is even larger than the IPv4, so every network must have an IPv6 prefix assigned.

For IPv6, subnets are allocated based on an even larger range that extends from /64 to /60 increments of /32 or bigger (the last segment is reserved). For convenience, you can assign two IPv6 /48 addresses as a /56, and it means each 128-bit subnet will use a single 128-bit value for network mask.

For example, if your provider provides you two /56 IPv6 addresses, the mask used for one is : 0f13:a4eb:1000:c001:5c01:1a09:2f00::/56. It means each 128-bit range needs 6 16-bit numbers for a network mask. So for an example, a /56 IPv6 prefix is expressed as this: (2001:0f13:a4eb:1::/56) (2001:0f13:a4eb:1::/64) (2001:0f13:a4eb:1::/128). 2001:0f13:a4eb:1::1. 64 bits.