IPv6 Adoption: Which Countries and TLDs Are Leading the Transition?

The IPv6 transition has been "happening" for over 25 years. RFC 2460 defined IPv6 in 1998. IANA allocated the last IPv4 blocks in 2011. And yet the internet industry has treated the shift from 4.3 billion IPv4 addresses to 340 undecillion IPv6 addresses with the urgency of a queue at the DMV. I wanted to know whether the DNS record data tells a different story — whether the transition is actually happening at the infrastructure level, even if slowly. So I processed 7 snapshots of Rapid7 Project Sonar forward DNS (FDNS) data covering November 2017 through April 2020, focusing specifically on AAAA records. What I found was a 9.35x increase — from 23.5 million to 219.7 million AAAA records in roughly 2.5 years. The transition isn't just happening. At the DNS layer, it accelerated dramatically.

How I Measured This

The data comes from Rapid7's Project Sonar, which conducted internet-wide forward DNS scans and published the results as open datasets. Sonar queried known hostnames and recorded the responses, including AAAA records — the DNS record type that maps a hostname to an IPv6 address. Where an A record points to an IPv4 address like 203.0.113.50, a AAAA record points to an IPv6 address like 2001:0db8:85a3::8a2e:0370:7334.

I processed 7 snapshots between November 2017 and April 2020, extracting every AAAA record, parsing the associated domain to identify its TLD, and aggregating counts by TLD and IPv6 prefix. The 2017-11-10 snapshot serves as my baseline, with each subsequent snapshot measured against it.

A few important caveats. Project Sonar's scanning methodology evolved over time — the jump between the November 2018 and April 2020 snapshots partly reflects expanded scan coverage, not just organic AAAA record growth. The 2017 snapshot is the cleanest for TLD-level comparison because the methodology was most consistent relative to the number of hostnames queried. I'll use 2017 data for TLD breakdowns and the full timeline for trend analysis.

Also, a AAAA record existing doesn't mean the IPv6 address is actively serving traffic. Some records are created automatically by DNS providers, some point to infrastructure that may or may not be reachable over IPv6. What AAAA records do represent is IPv6 readiness at the DNS layer — someone (or something) decided this hostname should be reachable over IPv6.

The Growth Trajectory

Here's the raw timeline across all 7 snapshots:

The standout is the June 2018 jump — a 71.3% increase in just two months. Something systemic changed between April and June 2018, and I'll get to what that was in a moment.

The overall trajectory from 23.5 million to 219.7 million represents a 9.35x multiplier in approximately 2.5 years. Even accounting for expanded scan coverage in later snapshots, the growth is significant. The early snapshots (November 2017 through April 2018), which share the most consistent methodology, still show steady 3-13% growth per period — suggesting organic AAAA deployment was already compounding before the mid-2018 acceleration.

For comparison, IPv4 A records in the same Sonar dataset were relatively flat over this period. The DNS namespace wasn't growing 9x — IPv6 records were being added to existing hostnames that previously only had A records.

Which TLDs Lead the Transition

The 2017 baseline snapshot gives the cleanest TLD-level picture. Here are the top 15 TLDs by AAAA record count:

The .com dominance at 45.6% is expected — it's by far the largest TLD. What's revealing is what comes next.

Germany's .de at 10.2% is the standout. With 2.4 million AAAA records, .de holds a larger share of IPv6-ready DNS records than .net (8.6%) despite .net having more total registrations globally. Germany's early IPv6 push wasn't rhetorical — it showed up in the DNS data. Major German hosting providers like Hetzner and German ISPs like Deutsche Telekom invested in IPv6 infrastructure earlier than most, and their customers' domains reflect that.

The Czech Republic (.cz) and Ireland (.ie) are punching well above their weight. Neither is a large ccTLD by registration count, yet both crack the top 15 for AAAA records globally. The Czech Republic's strong showing traces to CZ.NIC, the .cz registry operator, which has been an aggressive IPv6 advocate. They not only enabled IPv6 on their own infrastructure early but actively encouraged registrars to support it. Ireland's .ie presence likely reflects the concentration of major tech companies (many of which are IPv6-forward) hosting under the Irish ccTLD.

The presence of .io at position 13 is interesting for a different reason. The .io TLD is disproportionately used by tech companies and developer-focused products — exactly the demographic most likely to deploy IPv6 early.

You can inspect AAAA records for any domain using the DNS Inspector tool — just select the AAAA record type to see whether a domain has IPv6 addresses configured.

The Cloudflare Effect

The biggest single-factor explanation for mid-2018's explosive AAAA growth is Cloudflare. Here's what I found in the provider-level data:

In the 2017 baseline, Cloudflare-associated AAAA records were negligible. By the April 2020 snapshot, Cloudflare accounted for 1,176,091 AAAA records — a massive increase from near-zero in just over two years.

This aligns with Cloudflare's product timeline. In 2017, Cloudflare began enabling IPv6 by default for all customers on their free and Pro plans. By mid-2018, the rollout was largely complete. Every domain proxied through Cloudflare automatically received AAAA records pointing to Cloudflare's IPv6-capable edge network — regardless of whether the origin server supported IPv6.

This is the same pattern I've observed with DNSSEC adoption: provider automation is the dominant driver of protocol deployment. When Cloudflare decided that all domains on their network would be IPv6-reachable, millions of AAAA records appeared in DNS virtually overnight. The domain owners didn't make a conscious IPv6 decision. Cloudflare made it for them.

The June 2018 spike — a 71.3% jump in AAAA records in just two months — almost certainly reflects the tail end of Cloudflare's automatic AAAA rollout hitting the Sonar scan data. When a single CDN provider can move the needle on a global protocol transition by flipping a default, it tells you that IPv6 adoption is fundamentally a supply-side phenomenon. Domain owners don't deploy IPv6 — their infrastructure providers deploy it for them.

Google presents an interesting contrast. The 2017 snapshot showed 23,567 AAAA records associated with Google infrastructure, dropping to just 912 by 2020. This doesn't mean Google reduced IPv6 support — Google has been IPv6-native for years. Rather, it reflects how Google's infrastructure handles DNS differently. Google-hosted properties often use proprietary resolution paths that don't surface the same way in forward DNS scanning. The detection methodology matters.

Regional Patterns

The IPv6 prefix distribution from the 2017 data reveals clear regional patterns:

The RIPE region (Europe) shows 5.3x more AAAA-associated prefixes than ARIN (North America) and 17.7x more than APNIC (Asia-Pacific). This matches the TLD data — European ccTLDs dominate the adoption leaderboard beyond .com and .net.

Why Europe? Several reinforcing factors are at play.

IPv4 exhaustion hit RIPE first. RIPE NCC, the regional internet registry for Europe, exhausted its IPv4 pool in 2012 — years before ARIN (2015) and well before APNIC's practical exhaustion became acute. European network operators couldn't keep acquiring IPv4 addresses and were forced to invest in IPv6 earlier. That infrastructure investment filtered down to DNS records.

European registries were early IPv6 advocates. CZ.NIC (.cz), DENIC (.de), SIDN (.nl), and IE Domain Registry (.ie) all deployed IPv6 on their registry nameservers and actively promoted IPv6 compatibility among their registrar communities. When the registry infrastructure speaks IPv6, it creates a natural pull for downstream domains to follow.

Government mandates in Europe favored IPv6. Multiple European governments issued guidance or mandates for IPv6 deployment in government networks during the 2012-2016 period. While these mandates didn't directly affect commercial domains, they created a pool of IPv6-capable infrastructure and expertise that spilled over into the broader hosting ecosystem.

The relatively low APNIC number in 2017 is worth noting because Asia-Pacific — particularly India and Japan — has since become one of the fastest-growing IPv6 regions. India's massive mobile carrier Reliance Jio launched as an IPv6-only network in 2016, and by 2020 India had one of the highest IPv6 traffic percentages in the world. This mobile-driven adoption may not show up as strongly in AAAA records for traditional domain names, since mobile apps often use different resolution paths than browser-based domain lookups.

What's Driving Adoption

Looking across the data, three forces account for most AAAA record growth:

1. Provider automation. This is the biggest factor by far. When Cloudflare, Hetzner, OVHcloud, or any major hosting provider decides to enable IPv6 by default, thousands or millions of AAAA records appear without any action from domain owners. The mid-2018 spike is the clearest example, but the pattern is consistent: IPv6 adoption tracks provider policy, not customer demand.

This is the exact same dynamic I documented in my analysis of DNSSEC adoption. The providers who automate protocol deployment drive the numbers. The providers who leave it as an opt-in checkbox see near-zero uptake. The protocol itself is not the bottleneck — default configuration is.

2. Mobile carrier networks. The explosive growth of mobile internet in developing markets created IPv6 deployment at a scale that desktop-era networking never could. When T-Mobile US, Reliance Jio, or Verizon Wireless deploy IPv6-only or dual-stack on their mobile networks, every user on those networks generates IPv6 traffic. Content providers respond by adding AAAA records so their services are reachable over IPv6 without NAT64 translation overhead.

3. IPv4 address economics. IPv4 addresses became a traded commodity. By 2020, a single /24 block (256 addresses) traded for $20-30 per address. For hosting providers spinning up new infrastructure, deploying on IPv6 became the cost-effective path rather than purchasing increasingly expensive IPv4 allocations. The AAAA records in DNS reflect that economic pressure — new infrastructure increasingly launches with IPv6 first or dual-stack, rather than IPv4-only.

The Dual-Stack Reality

One pattern that's clear from the Sonar data is that the IPv6 transition is almost entirely additive. The overwhelming majority of hostnames with AAAA records also have A records. Pure IPv6-only deployments — where a hostname has a AAAA record but no corresponding A record — remain vanishingly rare in the public DNS.

This is the dual-stack approach in practice: keep IPv4 working for compatibility while adding IPv6 as an additional path. From a DNS perspective, it means a hostname resolves to both an IPv4 and an IPv6 address, and the client's operating system and network stack decide which to use (typically preferring IPv6 when available, per Happy Eyeballs / RFC 8305).

The dual-stack strategy is pragmatic but creates a long tail problem. As long as every IPv6-capable hostname also has an IPv4 fallback, there's no forcing function to complete the transition. IPv4 never becomes unreachable; it just becomes the slower, more congested, more expensive path. The transition completes through economics and friction rather than through a hard cutoff.

For DNS operators, dual-stack means maintaining both record types indefinitely. Every AAAA record deployment is additional configuration, not a replacement. The 219.7 million AAAA records in the 2020 snapshot represent 219.7 million hostnames that now need both A and AAAA records managed, monitored, and kept in sync.

What This Means for DNS Operators

If you're managing DNS infrastructure, the AAAA growth trajectory has practical implications.

Zone file sizes are growing. Every AAAA record added to a zone increases the zone file size. A AAAA record is 16 bytes versus 4 bytes for an A record, and the RDATA in zone files uses the full expanded text representation. For large zones with millions of records, the growth in AAAA records measurably increases zone transfer times, memory requirements for authoritative servers, and the time to propagate changes.

DNS response sizes increase. When a resolver queries for a hostname and receives both A and AAAA records (common with ANY queries or when resolvers pre-fetch both), the response packet is larger. This matters for UDP-based DNS because larger responses are more likely to exceed the 512-byte UDP limit, triggering TCP fallback or EDNS0 negotiation. The practical effect is slightly higher resolver load and marginally increased latency for dual-stack domains.

AAAA monitoring is now essential. If your domain has AAAA records — even if you didn't add them intentionally (your CDN or hosting provider may have) — you need to monitor them. An AAAA record pointing to a decommissioned IPv6 address creates a partial outage that only affects IPv6-capable clients, which is an increasingly large subset of users. These are notoriously difficult to debug because the site works fine for IPv4 clients, and most monitoring tools default to IPv4.

IPv6 glue records matter. If you run authoritative nameservers, their AAAA glue records in the parent zone are increasingly important. Some resolvers now prefer IPv6 when contacting authoritative servers, especially in regions with strong IPv6 deployment (Europe, parts of Asia). If your nameserver has a stale or missing AAAA glue record, you may see intermittent resolution failures that are difficult to diagnose.

The 9.35x growth I measured between 2017 and 2020 has only continued since. Major cloud providers (AWS, Google Cloud, Azure) now provision IPv6 by default for new resources. Cloudflare's automatic AAAA deployment covers an ever-growing share of the web. ISPs in Europe and Asia continue rolling out IPv6 to residential customers. The IPv6 transition at the DNS layer isn't a future event — the data shows it's been compounding for years, driven not by conscious adoption decisions but by provider defaults that make IPv6 the path of least resistance.