Available fields and functions

Filter expressions

A rewrite URL rule filter expression (that is, the expression that defines which incoming requests match the rule) can include the following fields:

• cf.edge.server_ip
• cf.edge.server_port
• cf.edge.client_port
• cf.zone.name
• cf.metal.id
• cf.ray_id
• cf.tls_client_auth.*
• http.cookie
• http.host
• http.referer
• http.request.headers
• http.request.headers.*
• http.request.accepted_languages
• http.request.method
• http.request.timestamp.sec
• http.request.timestamp.msec
• http.request.full_uri
• http.request.uri
• http.request.uri.*
• http.request.version
• raw.http.request.full_uri
• raw.http.request.uri
• raw.http.request.uri.*
• http.user_agent
• http.x_forwarded_for
• ip.src
• ip.src.lat
• ip.src.lon
• ip.src.city
• ip.geoip.*
• ssl

Refer to Fields for reference information on these fields.

Important

• To obtain the value of an HTTP request header using the http.request.headers field, specify the header name in lowercase. For example, to get the first value of the Accept-Encoding request header in an expression, use: http.request.headers["accept-encoding"][0].

• Use the to_string() function to get the string representation of a non-string value like an Integer value.

For information on the available functions, refer to Functions.

Rewrite expressions

A rewrite expression (that is, the expression that defines the dynamic URL rewrite to perform) can only include the following fields:

• http.request.uri.*
• http.request.headers.*
• http.request.accepted_languages

Refer to Fields for reference information on these fields.

The concat(), regex_replace(), and wildcard_replace() functions can appear only once in a rewrite expression.

Was this helpful?

What did you like?

Accurate

Easy to understand

Solved my problem

Helped me decide to use the product

Other

What went wrong?

Hard to understand

Incorrect information

Missing the information

Other

Thank you for helping improve Cloudflare's documentation!