The block list holds domains and link prefixes this server never wants to see; entries match as the whole domain, a host name or a link prefix. Well-known sites and shared platforms such as github.com cannot be blocked as a whole, but a specific link prefix on them can. The allow list stops threat feeds from matching a domain; reviewed exact links still match. Test a URL shows how a link is judged with these lists.
Example
/setup › Find a setting › Block list