Counting IPv6 One Query at a Time

Every device on the Internet needs a unique numerical address. Whether that address follows the decades-old IPv4 standard or the newer IPv6 format determines how that device reaches the rest of the network. IPv4 has been around since 1983 and still carries the bulk of traffic; IPv6, standardized in 1998, only began to see meaningful adoption in the last ten years. Estimates of global IPv6 usage vary from 30% to 40% depending on the measurement method.

Most published adoption figures, including those from Cloudflare Radar and APNIC, reflect the client side of the equation: how well Internet service providers have rolled out IPv6 to end users. Historical data from APNIC shows strong exponential growth through mid-2017, followed by a slower, linear climb that continues today. That leaves a significant blind spot — the server side. A client may be fully IPv6-capable, but if the server it wants to reach answers only over IPv4, the connection will fall back to the older protocol.

Cloudflare's public DNS resolver, 1.1.1.1, offers a way to look at both sides at once. Before any connection is made by name, the client must ask DNS for the server's address. Those lookups come in two flavors: A queries for IPv4 addresses and AAAA queries for IPv6 addresses. A client that has IPv6 available typically asks for both, then prefers IPv6 when the AAAA answer is non-empty — a behavior driven by the Happy Eyeballs algorithm.

A Baseline from the Client Side

Measuring client IPv6 adoption from a resolver's perspective is not as simple as counting how many clients reach 1.1.1.1 over IPv6. The resolver service is advertised with four addresses — two IPv4 (1.1.1.1 and 1.0.0.1) and two IPv6 (2606:4700:4700::1111 and 2606:4700:4700::1001) — but manual configuration often skips the IPv6 entries, which are harder to remember. Even when all four are set, many clients spread their DNS traffic across available addresses and still make some queries over IPv4.

A cleaner approach is to compare the volume of AAAA queries against A queries. Assuming IPv6-capable clients always request both record types, the share of AAAA queries serves as a proxy for client-side IPv6 readiness. On that basis, 1.1.1.1 data puts client-side IPv6 adoption at 30.5%. That is lower than the 35.9% observed from Cloudflare's HTTP traffic over the same period — a gap that is not unusual when comparing two different measurement perspectives.

  • 30.5% — client side, by DNS query volume
  • 35.9% — client side, by HTTP requests served

What the Server Side Shows

DNS answers also reveal how many servers are reachable over IPv6. When 1.1.1.1 returns a non-empty response to an AAAA query, that means the domain in question has published an IPv6 address. By this measure, server-side IPv6 adoption stands at 43.3% by query volume — noticeably higher than the client-side figure.

Caching behavior does not skew these numbers. A and AAAA records carry similar minimum TTLs in responses from 1.1.1.1, so neither record type is being cached longer at the client level in a way that would suppress queries for one or the other.

Combining Both Sides

Putting the two DNS-derived figures together gives a practical estimate of how often an IPv6-capable client can actually connect to a server over IPv6. If 30.5% of address lookups come from IPv6-capable clients, and 43.3% of those lookups receive an IPv6 answer, then roughly 13.2% of connections are likely to happen over IPv6.

Popular domains skew that number upward. For domains in Radar's Top 100 list, server-side IPv6 adoption reaches 60.8%. Removing those domains from the calculation drops the combined estimate from 13.2% to 8%. The Top 100 matters so much because it accounts for over 55% of all A and AAAA queries handled by 1.1.1.1. A handful of extra deployments among the most-visited sites would move the global number noticeably.

Where Adoption Goes from Here

IPv6 adoption can mean different things: counting capable users, capable devices, traffic volume in bytes, or the share of connections made over IPv6. Each perspective yields a different figure, and the full picture only emerges from considering several of them together.

  • 35.9% — client side, HTTP requests to Cloudflare's CDN
  • 30.5% — client side, A and AAAA queries to 1.1.1.1
  • 43.3% — server side, non-empty AAAA responses from 1.1.1.1

The gap between client and server adoption matters. For an IPv6-capable client, the protocol is only usable when the destination server also speaks it. The DNS perspective puts that combined rate at just 13.2% of connections — and at 8% when the most popular domains are excluded.

ISPs and hosting providers carry much of the responsibility for bringing client-side and server-side numbers up. But the largest content sources have an outsized role: 39.2% of queries for Top 100 domains still receive IPv4-only responses. If those domains enabled IPv6, the effect on observed adoption would be immediate and substantial.