The phrase you see most often in IPv6 proxy packages is "/64 subnet". This notation determines the size of the address set you hold and — far more importantly — its blocking behaviour .
How Many Addresses Is a /64?
IPv6 addresses are 128 bits. /64 notation says that the first 64 bits are the network part and the remaining 64 bits are the host part. Those remaining 64 bits amount to roughly 18.4 quintillion (1.8 × 10¹⁹) addresses — billions of times the entire IPv4 space.
Address abundance in IPv6 is so vast that the question "how many addresses do I have" loses its meaning. The meaningful question is: "how many different /64 blocks do I have?"
Why Is /64 the Blocking Unit?
A defence system cannot block individual addresses in IPv6 — an attacker can generate an unlimited number of new addresses within the same /64. That is why, in practice, the entire /64 block is treated as a single source.
This explains why, when buying an IPv6 proxy, the most critical question is not "how many addresses" but "how many /64s".
The claim of "billions of IPv6 addresses" is technically true but misleading in practice. If you have a single /64 block, then as far as defence systems are concerned you have a single IP.
Measuring Pool Diversity
If you have thousands of addresses but only a single /64 block, then in terms of diversity you hold a single IP.
/48 and Wider Blocks
Some defence systems are more aggressive and block at the /48 level. A /48 contains 65,536 /64s. In that case you need to take block diversity up one level:
For resilience, prefer /64 blocks that come from different /48s. Blocks within the same /48 can be blocked together.
When Buying an IPv6 Proxy
- How many different /64 blocks are provided? This is the real diversity metric.
- How many different /48s do the blocks come from? Protection against aggressive blocking.
- Are the blocks shared? If other customers also use the same /64, reputation is shared.
- Is there a block replacement policy? Is a burned block replaced?
- Which ASN is it registered to? A hosting ASN means low trust on IPv6 as well.
Suitable Use Cases
IPv6 is suitable
- High-volume data collection from IPv6-enabled targets.
- Cost-sensitive work that requires a large number of requests.
- IPv6 compatibility testing of your own infrastructure.
- Ad verification (on compatible platforms).
IPv6 is not suitable
- Targets that support IPv4 only.
- Work that requires genuine IP diversity (with a single /64).
- Account management and social media.
- Scenarios that require a high trust score.
Summary
In IPv6, the /64is both the standard subnet unit and the de facto blocking unit. The number of addresses within a block is meaningless in practice; real diversity comes from holding different /64 (preferably different /48) blocks. When buying an IPv6 proxy, ask "how many blocks", not "how many addresses". On compatible targets the cost advantage is very high. For product details, see our IPv6 proxy page .