IPv6‑Only vs Dual‑Stack Hosting: Choosing the Right Path for Websites, Email and SEO

IPv4 addresses are getting expensive, IPv6 adoption curves keep climbing, and almost every serious hosting or network planning discussion now includes one key question: should we go IPv6‑only or stay on a dual‑stack (IPv4+IPv6) model for the next few years? This is no longer a purely network‑engineering topic. Your decision directly affects who can reach your website, how reliable your email delivery is, and how search engines see (and crawl) your content. At dchost.com, we see this tension daily when helping customers design new stacks, migrate from legacy infrastructure or consolidate multiple servers. In this guide, I will walk through the real‑world trade‑offs between IPv6‑only and dual‑stack hosting for websites, email and SEO, and share the practical patterns we actually deploy on our shared hosting, VPS, dedicated servers and colocation environments.

Key Concepts: IPv4, IPv6, Dual‑Stack and IPv6‑Only in Plain Language

IPv4 vs IPv6 in one minute

IPv4 is the classic addressing scheme the internet grew up on (e.g. 203.0.113.10). The pool is effectively exhausted, which is why IPv4 addresses keep getting rarer and more expensive. If you want to understand the economics behind this, we explained it in detail in our article on why IPv4 address prices are hitting record highs and what you can do about it.

IPv6 is the newer protocol with a vastly larger address space (addresses look like 2001:db8::1234). It fixes IPv4 scarcity, enables cleaner network design and often performs better on modern mobile and ISP networks.

What is dual‑stack hosting?

Dual‑stack means your server has both IPv4 and IPv6 addresses, and your DNS publishes both A (IPv4) and AAAA (IPv6) records for the same hostname. Clients that support IPv6 will usually prefer IPv6; older or IPv4‑only clients will fall back to IPv4 automatically.

From the website owner’s point of view, dual‑stack feels simple: everyone can still reach you over IPv4, while IPv6‑capable users and search engines start using IPv6 immediately. This is why dual‑stack has been the default safe path for most hosting setups.

What is IPv6‑only hosting?

IPv6‑only hosting means your server has only IPv6 addresses. If you expose that server directly to the public internet, it is reachable only from IPv6‑capable clients. To keep IPv4‑only users working, you need a translation layer such as:

• NAT64 + DNS64 for outbound and sometimes inbound compatibility
• Reverse proxies or load balancers that have both IPv4 and IPv6 and forward to an IPv6‑only backend

We documented this model in a hands‑on way in our story about running websites on an IPv6‑only VPS with NAT64/DNS64 as the bridge to IPv4. It is powerful, but you must understand the trade‑offs before using it for public websites and email.

Who Can Actually Reach You? Reachability and User Impact

Global IPv6 adoption vs your real audience

Global IPv6 adoption is steadily increasing and in some countries has passed 40–50%. We have covered these trends in depth in our article on rising IPv6 adoption rates and what they mean for your infrastructure. However, IPv6 adoption is very uneven by country, ISP, enterprise network and mobile carrier.

For a public‑facing website, the core reachability rules today are:

• Dual‑stack: Both IPv4 and IPv6 users can reach you without any special translation. This gives maximum reach.
• Pure IPv6‑only (no translation): Only visitors whose network supports IPv6 will be able to connect. Corporate networks and legacy ISPs may still be IPv4‑only.
• IPv6‑only with an IPv4 front layer: If you put a dual‑stack reverse proxy, CDN or load balancer in front, IPv4 users connect to the front layer, which then talks to your IPv6‑only backend. From the user’s perspective, this behaves just like dual‑stack.

Practical consequences for different project types

Based on what we see on dchost.com infrastructure, here is how the choice plays out for common projects:

• Corporate and e‑commerce sites: These almost always need full reachability, including corporate networks and legacy ISPs. We strongly recommend dual‑stack on the public edge (A + AAAA records) even if your internal backends are IPv6‑only.
• Internal tools, APIs for mobile apps, staging environments: Often good candidates for IPv6‑only, especially if you control the clients or if everything is behind a VPN or private network.
• Developer test environments and cost‑sensitive labs: IPv6‑only can make a lot of sense because you avoid burning scarce IPv4 addresses while still testing real world traffic via NAT64/DNS64 or a dual‑stack reverse proxy.

For public websites, the critical question is simple: can any significant part of my audience be IPv4‑only? If yes, pure IPv6‑only without a front layer is usually too risky today.

Email on IPv6‑Only vs Dual‑Stack: Where Things Get Tricky

Receiving mail: MX, IPv6 and fallbacks

For receiving email, your DNS MX records can point to hostnames that have IPv4 (A), IPv6 (AAAA) or both. Most large mail providers today support both protocols and will happily deliver over IPv6 if it is available.

However, some older or more conservative mail systems still prefer IPv4, or are not fully tested over IPv6. If your mail server is IPv6‑only with no IPv4 MX, those senders might fail to connect or fall back to gateways that treat your domain as unreachable. That translates directly into lost email.

Our real‑world rule of thumb at dchost.com is:

• For domains that accept important business mail, use dual‑stack MX endpoints (both A and AAAA).
• If your actual mail server is IPv6‑only, place a dual‑stack SMTP proxy or smart host in front, which speaks IPv4+IPv6 to the outside and IPv6 to the backend.

Sending mail: reputation, blocklists and IPv6‑only pain points

For sending email, IPv6‑only gets even more nuanced. Some big mailbox providers are very strict about IPv6 sender reputation, DNS and reverse DNS quality. Others still have partial or inconsistent IPv6 policies. If you get anything slightly wrong, your IPv6 mail may silently go to spam or be deferred.

We wrote a dedicated field guide on this topic: Email deliverability over IPv6: PTR, HELO, SPF and blocklists. The most important operational lessons from that guide are:

• Always configure a correct PTR (reverse DNS) record for both IPv4 and IPv6 addresses. We also have a separate primer on what PTR / reverse DNS is and how it affects email delivery.
• Use consistent HELO/EHLO hostnames that match forward and reverse DNS.
• Publish proper SPF, DKIM and DMARC records that list both your IPv4 and IPv6 sending addresses if you use dual‑stack.
• Monitor blocklists that track IPv6 ranges, not only IPv4.

If you move to pure IPv6‑only sending with no IPv4 fallback, any remote system that does not accept IPv6 inbound mail will reject or defer your messages. For customer‑facing domains, that is usually an unacceptable risk today. Dual‑stack sending remains the practical sweet spot.

SEO and Crawlability: How Search Engines See IPv6‑Only vs Dual‑Stack

Can search engines crawl over IPv6?

Major search engines support crawling websites over IPv6. If your site is available only on IPv6, they can still index and rank it. However, there are three practical areas where dual‑stack is usually safer for SEO:

• Consistency of crawling infrastructure: Some SEO tools, link checkers and third‑party bots you rely on may still be IPv4‑only. If they cannot reach your content, you might miss broken links, performance regressions or technical SEO issues.
• CDN and HTTP feature support: Many of the modern performance features that affect Core Web Vitals (HTTP/2, HTTP/3, TLS tuning, caching) are implemented at the edge or CDN. Those edges are almost always dual‑stack, even if your origin is IPv6‑only.
• Off‑site embeds and webhooks: Payment gateways, analytics beacons or headless CMS webhooks might still expect an IPv4 endpoint and affect conversions if they cannot connect.

If you are already working on performance and SEO from the hosting side, you might have read our guide on how HTTP/2 and HTTP/3 affect SEO and Core Web Vitals when you choose hosting. The key takeaway is the same: search engines reward speed, reliability and reach. IPv6 vs IPv4 is mostly invisible to them, as long as they can crawl your pages quickly and consistently.

Does IPv6 itself give an SEO boost?

There is no public evidence that “having IPv6” gives an automatic ranking boost. Instead, IPv6 is a technical enabler for:

• better network paths on modern mobile and ISP networks
• less NAT and fewer middleboxes, which can reduce latency
• easier scaling of infrastructure (more addresses, cleaner routing)

These factors can indirectly improve SEO if they translate into faster TTFB, LCP and availability. We explored this correlation in our article on how hosting infrastructure affects Core Web Vitals. The protocol version (IPv4 vs IPv6) is less important than the final user experience.

Practically, dual‑stack gives you the best of both worlds: IPv6 advantages where available, with IPv4 still there to avoid reachability gaps that could hurt traffic and conversions.

When IPv6‑Only Makes Sense (and When It Does Not)

Good candidates for IPv6‑only infrastructure

At dchost.com we see several patterns where IPv6‑only backends are an excellent fit:

• Private microservices and internal APIs: Services that are never exposed directly to the public internet, only to other servers over internal VLANs, VPNs or overlay networks.
• Container clusters and service meshes: K8s or K3s clusters where each pod gets its own IPv6 address, and a dual‑stack ingress acts as the edge. The public never sees the internal IPv6‑only design.
• Lab, test and CI environments: You can run entire staging stacks IPv6‑only, connecting to the outside world via NAT64/DNS64 or a dual‑stack gateway, and save scarce IPv4 addresses for production.
• Cost‑sensitive or address‑constrained deployments: Where obtaining additional IPv4 addresses is painful or expensive, moving more servers to IPv6‑only and keeping a small pool of dual‑stack edges is very efficient.

Our own experience accelerating IPv6 adoption without breaking anything is documented in The calm sprint to IPv6, and the architecture we recommend most often is “IPv6‑everywhere inside, dual‑stack at the edge”.

Where pure IPv6‑only (no IPv4 edge) is risky

Going fully IPv6‑only on the public edge without any IPv4 termination is still risky in 2025 for:

• Customer‑facing websites and e‑commerce: Any IPv4‑only user sees your site as down. That can be a measurable revenue loss, especially in B2B segments and certain regions.
• Public SaaS apps: Corporate firewalls and proxies are often conservative and IPv4‑only. Your app may be unreachable from entire organisations.
• Business email domains: Not all counterparties accept IPv6 mail, and misconfiguration can lead to silent delivery failures that are hard to debug.

In these cases, we strongly prefer to keep dual‑stack on the public MX and HTTP/HTTPS endpoints, even if the underlying application servers and databases are IPv6‑only.

Real‑World Patterns We Recommend at dchost.com

Pattern 1: Classic dual‑stack hosting (simple and robust)

This is the easiest pattern for most users:

• Your shared hosting account, VPS or dedicated server at dchost.com receives both an IPv4 and an IPv6 address.
• DNS publishes A and AAAA records for your domains.
• Your web server and mail server listen on both protocols.

Pros:

• Maximum compatibility; minimal surprises.
• Easy to reason about logs, firewall rules and monitoring.
• SEO and email tools continue to work as expected.

Cons:

• Each public service still needs at least one IPv4 address.
• Less pressure to modernise internal networks and address plans.

Pattern 2: Dual‑stack edge, IPv6‑only origin

In this pattern you combine the best of both worlds:

• Public DNS and TLS endpoints (reverse proxies, load balancers, WAFs) are dual‑stack and reachable over IPv4 and IPv6.
• Application servers, caches, and databases run on IPv6‑only networks behind them.

This is increasingly our favourite pattern for new VPS and dedicated deployments. It minimizes IPv4 usage while keeping your users and search engines happy. It also plays nicely with modern DevOps flows, CI/CD and service discovery. If you want a very practical checklist for the DNS side of this, see our guide Ready for IPv6? My no‑drama dual‑stack playbook for AAAA records and real‑world tests.

Pattern 3: IPv6‑only lab with NAT64/DNS64 for outbound

For internal labs or developer sandboxes on our VPS or dedicated servers, we often suggest fully IPv6‑only networks with:

• NAT64/DNS64 to let IPv6‑only servers reach IPv4‑only external services (package repositories, APIs, etc.).
• No public IPv4 except possibly a single bastion or VPN endpoint.

This drastically reduces IPv4 consumption while letting teams build and test the same stacks they will run in production, including IPv6‑specific firewall policies and monitoring.

A Practical Migration Roadmap: From IPv4‑Only to Dual‑Stack or IPv6‑Heavy

Step 1: Audit your current dependencies

Before touching DNS records, list the external systems that must reach you or that you must reach:

• Payment gateways, CRM, ERP, shipping APIs
• External SMTP relays, newsletter tools and ticketing systems
• Monitoring services and uptime checkers
• CDN or WAF providers, if used

Check which of them support IPv6 today. For anything critical that is still IPv4‑only, plan an IPv4‑capable front layer (reverse proxy, mail relay or VPN exit) even if your internal servers are IPv6‑only.

Step 2: Enable IPv6 on your hosting or VPS

On dchost.com shared hosting, VPS and dedicated servers, IPv6 support is available in our infrastructure and can be enabled per service. For a VPS, the high‑level steps are:

• Assign at least one IPv6 address (or a small subnet) to your server.
• Configure the OS network settings (Netplan, NetworkManager or classic networking).
• Open the appropriate IPv6 ports in your firewall (nftables, ufw, firewalld, etc.).
• Ensure your web server and mail daemons listen on both IPv4 and IPv6.

We wrote a detailed walk‑through for this in our IPv6 setup and configuration guide for your VPS server.

Step 3: Add AAAA records and test dual‑stack

Once IPv6 connectivity is working at the OS level, you can:

• Add AAAA records for your main hostnames (www, api, mail).
• Keep A records in place so IPv4 users remain unaffected.
• Test from multiple networks: mobile (often IPv6‑first), home ISP, corporate VPNs.
• Use tools like ping6, traceroute6 and online IPv6 checkers to verify reachability.

Monitor your logs to confirm some fraction of traffic is now arriving via IPv6. You should not see an increase in HTTP error rates or email bounces simply from enabling dual‑stack.

Step 4: Gradually move internal services to IPv6‑only

Once your public edge is dual‑stack and stable, you can safely experiment with IPv6‑only for internal components:

• New application servers with only IPv6 addresses, behind a dual‑stack reverse proxy.
• Cache servers (Redis/Memcached) and databases that live only on IPv6 networks.
• Internal APIs that you control entirely, with no public exposure.

If you already apply other best practices (like separate caching, background jobs and correct PHP configuration), this is a natural evolution. For example, our guides on WordPress object caching with Redis or Memcached and tuning PHP‑FPM for WordPress and WooCommerce fit neatly into an IPv6‑heavy, dual‑stack‑edge architecture.

Step 5: Revisit email and DNS after each change

Email and DNS are where subtle mistakes hurt the most. After any network or IPv6 change:

• Verify MX records still point to reachable, dual‑stack endpoints.
• Check SPF, DKIM and DMARC records reference the correct IPv4 and IPv6 senders.
• Confirm PTR (reverse DNS) is correct for any new addresses.
• Send test messages to major providers and check spam folders and headers.

Think of this as part of your regular hosting hygiene, just like your SSL/TLS updates or backup tests.

Summary: How to Decide Between IPv6‑Only and Dual‑Stack for Your Next Move

If we compress everything above into a practical checklist, the picture becomes much clearer. For public websites and business email, dual‑stack on the public edge is still the safest, lowest‑friction choice in 2025. It gives you maximum reach across IPv4‑only and IPv6‑capable networks, while letting you start reaping IPv6 performance and routing benefits immediately. Under the hood, you can push more of your infrastructure (app servers, caches, databases, internal APIs) to IPv6‑only and use NAT64/DNS64 or dual‑stack proxies as needed to talk to the remaining IPv4 world. That is the architecture we are building and recommending every day on dchost.com shared hosting, VPS, dedicated and colocation platforms.

Pure IPv6‑only at the edge can be appropriate for controlled environments and internal tools, but is still too risky as the only public entry point for most businesses. If you are planning a new project or a migration and want to rationalize IPv4 usage, improve performance and keep SEO and email stable, we are happy to help you design a dual‑stack‑friendly, IPv6‑ready setup that matches your real traffic profile. Reach out to our team, tell us about your website, email and SEO priorities, and we will help you choose the right combination of IPv6‑only components and dual‑stack edges on dchost.com infrastructure.