Verify Force.com Experience Cloud Site with Facebook | Salesforce
Salesforce owns the force.com domains, so you have two options for preparing your Experience Cloud site for Facebook domain verification. First, if you have a custom domain, like https://www.example.com, that points to your site, you can update your domain's DNS record so that you can verify it with Facebook. If you don’t have a custom domain, don't worry! By updating your site’s metadata, you can verify your force.com domain with Facebook and claim it as your own.
Below Facebook links for reference:
/ domain-verification
/ verifying-your-domain
Below link to know about domain verification with google:
https://support.google.com/webmasters...