Changing Your Free Wix URL

Yes. You can connect a domain that you already own after upgrading your site.

Upgrading does not automatically change your domain to a custom domain. Instead, you can either connect a domain you already own, or purchase a new domain from Wix.

No. Each site you want to upgrade requires its own site plan. If you want to upgrade multiple sites in your Wix account, you’ll need to purchase multiple site plans. 

As a promotional gift, you receive a one year free domain voucher with the initial purchase of selected yearly Premium or Studio site plans.

Generally speaking, it is not possible to remove 'www' from your domain name, as it is part of a web address' structure. This is true for all custom domains. 

Your site visitors may leave out the 'www' prefix when entering your site's web address, for example 'mystunningwebsite.com'. They will still reach your site, but the URL in their browser automatically updates to show the 'www' part.

Free Wix URLs work differently. They don't use the 'www' prefix.
Therefore: 

The Site URL prefix part of your free Wix URL is specific to your account. If you transfer your site to another account, the site URL prefix part of the URL will change. 

For example:
Paul's site URL prefix is PaulSiteBuilder, and he built a site and named it MyAwesomeSite. The free Wix URL will be paulsitebuilder.wixsite.com/myawesomesite.

Paul transfers the site to Jennifer, and her site URL prefix is JenniferSiteManager. Once Jennifer accepts the site transfer, free Wix URL becomes: jennifersitemanager.wixsite.com/myawesomesite.

The new site owner can change both the site URL prefix and site address from their own account settings. However, you cannot use the same site prefix as another Wix account.