This feature is available with some paid plans
When you add a custom domain to your account, you're given the option to make it available for use in all of your groups or just certain ones. To add it to additional groups later (for example, because you created a new group), follow these steps.
To add a custom domain to a group:
- Log in to your Bitly account.
- Click Settings in the left sidebar.
- Click Groups under Account settings.
- On the group details page, click Add Custom Domain.
- Select one or more custom domains.
- Click Save Domains.
You can follow these steps to add your custom domain to as many groups as you'd like.