All annual billing plans are eligible for one free custom domain for the first year of service. Custom domains are not free for subscribers on monthly billing plans, but can be purchased directly from Squarespace. Learn more about claiming and purchasing Squarespace domains here.
If you have purchased a domain from a third-party provider, and would like to map those domains to your Squarespace site - you will need to update your DNS settings managed by the third-party provider. Click here for more information.