IPv6 support

Fastly has integrated IPv6 into its technology stack. By enabling IPv6, visitors on IPv6 connections can access your websites and applications. This can be done without any changes to your backend infrastructure.

Enabling IPv6

To enable IPv6, follow the instructions below as appropriate for your CNAME record.

Enabling IPv6 on Non-TLS- and TLS-enabled hostnames

You can enable IPv6 dualstack (IPv4 and IPv6) functionality for your hostname by prefixing your CNAME record with dualstack. For example, if you're on our "g" shared SAN certificate, you have the following dualstack options:

  • dualstack.g.shared.global.fastly.net (dualstack global map for HTTP/2 support)
  • dualstack.g.shared.us-eu.fastly.net (dualstack US-EU map for HTTP/2 support)
  • dualstack.g.ssl.global.fastly.net (dualstack global map for HTTP/1 only)
  • dualstack.g.ssl.us-eu.fastly.net (dualstack US-EU map for HTTP/1 only)

Enabling IPv6 on customer-specific hostnames

If you use a customer-specific hostname, contact Fastly Support and we'll provide you with an IPv6 map or enable your current one. By default, maps will be HTTP/2 enabled and have a global billing region set. Be sure to specify any required changes when having a new map created.

Enabling Anycast IPv6 addresses for apex domains

If you use our Anycast IPv4 addresses for apex domains, contact Fastly Support and we’ll provide you with the appropriate Anycast IPv6 addresses.

Geolocation features for IPv6

Fastly's geolocation features work with IPv6 addresses.

VCL variable

You can track whether a request came in as an IPv6 request with the req.is_ipv6 VCL variable as well as by the IPv6 format itself when logging %h.

Testing IPv6

Once you’re up and running with IPv6, test IPv6 by entering a dig command in a terminal application to make sure your map returns AAAA records. For example, you can type something similar to this:

dig www.example.com AAAA +short

where www.example.com is the domain that you’re testing.

Your output should appear similar to the following:


You can also use a tool like What's my DNS and choose the AAAA option to see how clients around the world are resolving to your CNAME record.

Performance implications

Enabling IPv6 shouldn’t negatively impact performance. Most modern clients implement an approach called Happy Eyeballs to connect over either IPv4 or IPv6, whichever is faster. Happy Eyeballs chooses IPv6 over IPv4 when all else is equal.

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