# Are IPv6 proxies good? Why a /64 is one house > IPv6 proxies are cheap because addresses are plentiful, but sites that score IPv6 count a /64 prefix as one household. Many addresses from one prefix are one. Source: https://mosaicbrowser.com/blog/ipv6-proxies-and-subnets ## IPv6 proxies, and why a site may count a /64 as one house IPv6 proxies are cheap because addresses are plentiful, but sites that score IPv6 count a /64 prefix as one household. Many addresses from one prefix are one. ![/64: Many addresses, one /64, one household, beside a screenshot: a proxy provider in Mosaic: one gateway line that mints a separate session for every profile](https://mosaicbrowser.com/covers/ipv6-proxies-and-subnets.webp) IPv6 proxies can be good, but not for the reason they are sold. The pitch is volume: millions of fresh addresses for the price of a few IPv4 ones. A site that scores IPv6 does not count addresses, though. It counts prefixes, because a single home is usually handed a whole /64 or more, and every device in it can pick any address inside. Many fresh addresses from one /64 look like one household, not many people. ## Why one house has billions of addresses An IPv6 address is 128 bits. By convention the first 64 are the network and the last 64 are the interface, the device. A home router gets a prefix from the ISP and announces a /64 on the local network. Each phone and laptop then makes up its own last 64 bits, usually with privacy extensions that pick a new random value every so often, so the same laptop shows a site a different address from one day to the next. ISPs also hand out more than one /64. RFC 6177, the IETF's advice on how much space an end site should get, stopped recommending a /48 for everyone but still says a home should get more than a single /64, so it can run more than one network. In practice a household may hold a /64, a /60 or a /56, depending on the ISP. So the address a site sees tells it less than an IPv4 address would. The last 64 bits change on their own. The prefix stays. Mosaic is a desktop app Email yourself the link and open it on your computer. [How it works: Provider minting](https://mosaicbrowser.com/features/proxy-providers) ## How sites count IPv6 Think about what that means for anything that rate-limits, blocks or scores by address. Blocking one IPv6 address is pointless when the same machine can pick another in milliseconds. So systems that take IPv6 seriously aggregate it: by /64 at least, often wider, up to the whole block an ISP or hosting company was assigned. A reputation list that flags one address in a /64 tends to colour the neighbours too. For a person running several accounts they are entitled to run, say an agency with one profile per client, that has a plain consequence: | What your profiles exit from | What a prefix-scoring site sees | | --- | --- | | Ten addresses in one /64 | one network, one household | | Ten addresses in one hosting company's /48 | one datacentre customer | | Ten residential exits in ten ISPs' prefixes | ten households | The first two rows are what a cheap IPv6 package often is: one block, carved into as many /128s as you want to buy. The address count on the invoice is real. The number of places those addresses come from may be one. ## When an IPv6 proxy is the right tool It works best when three things are true. The sites you need publish an IPv6 address (many still publish only IPv4, and an IPv6-only exit simply cannot reach them). Each exit you use sits in its own prefix. And the network it belongs to is one a person would plausibly browse from, which a hosting company's block usually is not. A dual-stack residential exit is a different thing from a sold IPv6 block. It is someone's home connection with an IPv4 address and a prefix, and a site that reaches it sees whichever family the connection used. Our own proxy check once read that pair as a rotating pool, three checks in a row, before we taught it that [an IPv4 and an IPv6 address from one proxy is one exit](https://mosaicbrowser.com/blog/dual-stack-proxy-two-addresses). ## Checking whether two exits share a /64 Expand any `::` shorthand and compare the first four groups. These two (documentation addresses) are the same network: ``` 2001:db8:7c3e:5dc4::d565 2001:db8:7c3e:5dc4:91a0:2b17:4c0e:8f33 ``` These two are not, though they share a /48: ``` 2001:db8:7c3e:5dc4::d565 2001:db8:7c3e:9a10::12 ``` Do the same with your own connection. If an IPv6 address on a proxy check shares its first four groups with the address your machine shows with no proxy, a request went around the proxy. WebRTC is the usual way that happens, because it gathers candidates over UDP that an HTTP proxy never carries ([the candidate your proxy never carried](https://mosaicbrowser.com/blog/webrtc-ipv6-candidates)). ## What Mosaic does with IPv6 exits Mosaic's proxy check samples the exit twice, a location lookup and a tunnel probe, and compares the two addresses only within one family. An IPv4 and an IPv6 address from two probes are not evidence that the exit moved, because they cannot be compared at all. It does not group exits by prefix for you. Two saved proxies on one /64 are, to Mosaic, two addresses. So the prefix check above is yours to make before you trust a block to separate accounts. The way Mosaic does help is upstream of that: paste a seller's gateway line as a provider and every profile mints its own session id, so each profile asks the seller for its own exit instead of sharing one ([forty profiles, forty exits](https://mosaicbrowser.com/blog/forty-profiles-forty-exits) has the measurement). Whether those exits land in different households is the seller's pool, and it is worth reading a few of them by hand before relying on it. ## Questions ### Are IPv6 proxies good? They are good when the sites you need reach over IPv6 and each exit sits in its own prefix on a plausible network. They are weak when a seller hands out many addresses from one /64 or one datacentre block, because a site that scores IPv6 counts the prefix, not the address. ### What is a /64 in IPv6? The first 64 bits of an address, the network part. One home or office network is normally one /64, and every device on it picks its own last 64 bits, so a single household can use a practically unlimited number of addresses inside it. ### Why are IPv6 proxies so cheap? Because addresses cost almost nothing. One /64 holds about 18 quintillion of them, so a seller with a single block can sell what look like millions of different IPs. To a site that groups by prefix, most of them are the same place. ### Can an IPv6 proxy load every website? No. An IPv6-only exit cannot reach a site that publishes only an IPv4 address. A dual-stack exit can reach both, and a site then sees whichever family that connection used. ### How do I tell if two IPv6 addresses share a /64? Compare the first four groups of hexadecimal digits, after expanding any :: shorthand. If they match, the two addresses are on the same /64 network. ## Related [An IPv4 and an IPv6 address from one proxy is one exit](https://mosaicbrowser.com/blog/dual-stack-proxy-two-addresses): A proxy that shows both an IPv4 and an IPv6 address is a dual-stack exit. Sites see either one, so look both up before you trust the location. [WebRTC and IPv6: the candidate your proxy never carried](https://mosaicbrowser.com/blog/webrtc-ipv6-candidates): A WebRTC IPv6 leak is a candidate gathered over UDP that an IPv4 proxy never sees. Blocking non-proxied UDP closes it for both address families at once. [Same proxy session on multiple profiles: forty profiles, forty exits](https://mosaicbrowser.com/blog/forty-profiles-forty-exits): The same proxy session on multiple profiles means one exit IP for all of them. A batch of ours did it in September 2026; now every profile mints its own. [Residential proxy: an exit on a home internet connection](https://mosaicbrowser.com/glossary/residential-proxy): A residential proxy sends your traffic out through an address an ISP assigned to a home connection, so sites see a household rather than a data center. [Provider accounts: one gateway line, one exit per profile](https://mosaicbrowser.com/features/proxy-providers): Paste your proxy seller's gateway line once and Mosaic mints a separate session for every profile, so each one browses from its own exit address. [Detecting a proxy with two clocks](https://mosaicbrowser.com/blog/proxy-detection-by-latency): A server times the TCP handshake to the exit and a round trip to the browser. Behind a proxy the second is longer, and the gap is the tunnel. ["Unlimited bandwidth" proxies and where the limit really is](https://mosaicbrowser.com/blog/unlimited-bandwidth-proxies): An unlimited bandwidth residential proxy still has a limit. It moves to threads, ports, speed or a fair-use clause, and the terms say which one. [The proxy bill is usually bigger than the browser bill](https://mosaicbrowser.com/blog/proxy-bill-bigger-than-browser): Past a couple of dozen profiles, the exits cost more each month than the anti-detect browser. That is why we price per month, not per profile. ## Mosaic, on your own computer The browser this blog is about: its own Chromium, fingerprints from real machines and a proxy exit per profile. Free holds 3 profiles. Pro is $49 a month for any number. Mosaic is a desktop app Email yourself the link and open it on your computer.