Do you support custom CNAME endpoints?


Yes, Ably provides an option with our Committed Use packages to have custom CNAME endpoints. Customers using our CNAME feature can also benefit from our Active Traffic management service.

Currently, all of our Ably client libraries connect to two endpoints by default:

Additionally, if an Ably client library is unable to connect to a data centre due to a network partitioning, DNS or routing issue, our client libraries automatically use fallback hosts to work around these types of issues and ensure that the client can still connect to an alternate data centre.  In these cases, the client library will connect to a host name such as or


There are two possible setups for implementing a Custom CNAME endpoint:

Custom domain is an Ably subdomain: 


For these we use Ably's existing wildcard certificate supporting * and *

Custom domain in a Customer subdomain:


We issue the certificate, based on you configuring a CNAME DNS record or other record on * being added that authorises issuing a certificate for that subdomain. That means that the setup only needs to be done once, and doesn't require any additional manual intervention each time the certificate needs renewal.

This approach is also much less risky than handing out the wildcard * certificate.

As an example, here is how this would work:

  • is used for the primary endpoint
  • [a-e] is used for the fallback domains
  • We issue a cert for and *, and it's a CNAME DNS record set up by the customer for that subdomain.

In addition, we then handle all renewals of certs, rolling out to our global endpoints, load balancers etc, without ever having to coordinate with you manually to get new certs issued. This works well for both parties.

Note: By default, Ably serves fallback traffic under the * domain which is managed separately to the main * domain. This means even problems at the DNS or registrar level on the primary domain can be routed around using the fallback mechanism.

When using your own custom domain, we provide these DNS records for you to CNAME to. Whilst we recommend you implement a similar architecture by using CNAMEs under two different domains (e.g. for your primary traffic and for your fallback traffic, with the latter hosted with a different registrar and using different name servers to the first), that is not required. Therefore, the decision as to whether you need that extra level of redundancy within your own DNS system is your choice.

Please get in touch with us if you would like a custom CNAME end-point for your company so that we can create a premium package for you and advise on pricing.