Some external services require you to prove control over your domain name. You can now verify your domain name from the Domains Setup page.
Where: This change applies to Lightning communities accessed through Lightning Experience and Salesforce Classic in Enterprise, Essentials, Performance, Unlimited, and Developer editions.
Why: External services use various methods to prove domain ownership. Some external services, such as Sign In with Apple, provide you with a verification file that you download to your computer. Store the file on your domain at a location specified by the external service. If the service can locate the file, your domain is verified.
How: You verify your My Domain or community domain from the Domains Setup page. Next to the domain, select Verify, and then choose the verification file that you downloaded from the external service. Salesforce then stores the file at the location specified by the external service.