How to Allow Browsing of Only Certain Web Sites?
In case you need to allow browsing of certain web sites only, use the predefined Locked policy of Web Safety. This policy contains URL specific regular expression blocking access to any URL .* in Web Filter / Policies / Locked / Filtering Rules / Domains and URLs. Add the needed site to the exlusion list for this policy and click Save and Reload.
Try browsing to the needed site and see what additional domain names need to be excluded. Add them to the exclusions list too. For example, if we would like to limit browsing to youtube.com only then Locked policy need to contain the following domain name exclusions: