Referrer is

Matches when the Referer request header matches one or more specified wildcard patterns.

This condition inspects the Referer request header to determine if it matches a specified list of wildcard patterns. It returns true if the header value matches any of the defined patterns.

Configuration

  • Case sensitive: Whether to enable case sensitivity during the comparison. When disabled, the condition performs a case-insensitive match against the Referer header sent in the request.
  • Referrer pattern: The input field used to add new wildcard patterns. Multiple entries can be added simultaneously by separating them with a comma, a pipe (|), or a new line.
  • Defined patterns: The list of all active patterns for this condition. The condition returns true if the requester’s referrer matches any entry in this list.

Pattern matching

The system supports flexible wildcard entries to simplify configuration. To ensure comprehensive matching, the system automatically translates wildcard entries into optimized regular expressions during processing:

  • Automatic conversion: Hostname-only patterns (e.g. *example*) are automatically converted to *://*example* to match any protocol.
  • Explicit patterns: You may provide full URLs or specific paths using wildcards (e.g. https://example.com/path/*).

Measurement

The condition extracts the Referer header from the incoming request and evaluates it against the Defined patterns.

  • Match found: If the header value matches any pattern in the list, the condition returns true.
  • No match found: If the header value matches none of the patterns, the condition returns false.
  • Missing header: If the Referer header is absent from the request, the condition returns false.

Performance

  • Sequential validation: Evaluation time increases incrementally with the number of patterns in the list. For requests that do not match any pattern, the system must evaluate every entry before returning false.
  • Short-circuit optimization: The condition iterates through the list and returns true as soon as the first match is identified. To minimize processing time, place the most frequently matched patterns at the top of the list.

Last modified March 5, 2026