Is a Local Host, Development Server, or Use of an IP Address Supported by Your Service? [Legacy Customers]
Yes, "localhost" is allowed by default without the need to explicitly add it to your project. If you are using an IP address or a different name for your local/development environment, you may add these to your web font project's domain list to allow them.
As an additional note, when adding these types of servers, you do not need to add port numbers; only the IP address or server name itself.