Assigning a custom subdomain to a Fly app

I deployed an app to Fly and decided to point a custom subdomain to it.

My fly app is

I wanted the URL to be (see issue #1524).

Relevant documentation: SSL for Custom Domains.

Assign a CNAME

First step was to add a CNAME to my domain.

I pointed CNAME of at using Vercel DNS:


Issuing a certificate

Fly started serving from as soon as the DNS change propagated. To get https:// to work I had to run this:

% flyctl certs create 
Your certificate for is being issued. Status is Awaiting certificates.

I could then run this command periodically to see if it had been issued, which happened about 53 seconds later:

apache-proxy % flyctl certs show
The certificate for has been issued.

Hostname                  =

DNS Provider              = constellix

Certificate Authority     = Let's Encrypt

Issued                    = ecdsa,rsa

Added to App              = 53 seconds ago

Source                    = fly

Created 2021-11-20T12:46:43-08:00 · Edit