Do you want your computer to treat a domain as localhost? You can map it
as such in your /etc/hosts file. For example, if I have an web app that
refers to itself with the dev.app.com domain, I can add the following line
to my /etc/hosts file to make sure the domain resolves to localhost:
127.0.0.1 dev.app.com
Now, if I pop open my browser and visit dev.app.com:3000, I will see
whatever is being served to localhost:3000.
h/t Chris Erin