The Cloudflare Rules language is a flexible and intuitive specification for building rule expressions. Based on the widely known Wireshark display filters, the Rules language allows you to precisely target HTTP requests with a syntax and semantics familiar to security engineers.
When evaluating a rule, Cloudflare compares values associated with an HTTP request to those defined in the rule’s expression. If the expression evaluates
true, Cloudflare triggers the action for that rule.