The easiest way to make your Project available via HTTPS on its custom domain is with Cloudflare, which has a free tier that provides HTTPS.

Cloudflare requires you to change your nameservers to point to them. Meaning that the DNS records are then handled on the Cloudflare side. When you’re setting up the site in Cloudflare, you’ll need to make sure those A records point to the CodePen IP Addresses 52.10.184.195 and 52.40.196.217.

Cloudflare setup with A records

You’ll also need to set your SSL/TLS setting to Flexible.

Once you’ve got the site all set up in Cloudflare and the DNS changes have propagated (this may take up to one day), you’ll be able to view your site in HTTPS.

It’s up to you to only use secure resources to keep that “Secure” light green!

Host-Specific Notes