When you create a kit, you will be asked to specify the domains on which that kit will appear. Typekit will only work when loaded from one of these allowed domains; you can edit this list of domains at any time. In your kit editor, click on “kit settings” in the upper right; you can specify multiple domains by separating them with a comma. Each kit permits you to add up to ten domains.
You can use wildcards to include all subdomains from a particular domain. For example, you could add “*.domain.com” to use the kit on all subdomains under domain.com.
You can also add “localhost” to the list of allowed domains to enable Typekit to work from a local web server; read more about developing locally. Or, you can add your development server, e.g., dev.domain.com.