Using custom subdomain with GitHub repositories
GitHub actually allows you to host websites for your projects directly from the repository itself. It will have URL something like https://<username>.github.io , you can add your custom domain to it too. If you haven’t done it, GitHub has pretty good documentation about it. You can read it here.
Now, let’s suppose you have already set up a custom domain and your default site is accessible through https://example.com. Now, if you create a new repository named project , and enable GitHub pages, it will be accessible through https://example.com/project but sometimes it makes more sense to have a custom sub-domain, like https://project.example.com. To do this, there are some additional configurations required. Just follow the steps below.
To make the steps more clear, I will use my own, recent project example for which I set up the custom subdomain. My GitHub username is DefCon-007 and my personal website which was available through GitHub pages at https://DefCon-007.github.io is served from my custom domain with https://defcon007.com and https://www.defcon007.com](https://www.defcon007.com). I now had a new repository named utilobot-website which contained some HTML and was served at https://defcon007.com/utilobot-website and I wanted it to be served at https://utilobot.defcon007.com.
Step 1: Configure DNS settings
Go to your domain provider’s website and add a new CNAME record with name as your subdomain and value as your GitHub root URL with a trailing dot. In my case the name was utilobot and the value was defcon-007.github.io. The dot at the end is not a typo!
Step 2: Add CNAME file
Now, add a new file named CNAME to your repository with just a single line in it, that is your complete URL.
You can also go to the repository settings and enter your custom domain in the GitHub Pages section, it will automatically add the CNAME file.
That’s it, you have a custom domain for your GitHub project now. Try opening it with http first, and it is working fine, you can select Enforce HTTPS option in the repository settings page.
Thanks for reading.