Use the following rule to match a host or a domain, for example, https://www.domain.com

Rule type: Content Matching

Match Type: Regular Expression

Header Field: Host

Match String: /^www\.domain\.com$/

Ignore Case: enabled

Match field

Start Regex: /

Start Match: ^

Regular text: www

Literal character: \.

Regular text: domain

Literal character: \.

Regular text: com

End Match: $

End Regex: /