modifyIncomingRequestHeader

Property Manager name: Modify Incoming Request Header
Behavior version: The v2025-10-16 rule format supports the modifyIncomingRequestHeader behavior v1.2.
Rule format status: GA, stable
Access: Read/Write
Allowed in includes: Yes

Modify, add, remove, or pass along specific request headers coming upstream from the client.

Depending on the type of action you want to perform, specify the corresponding standard header name, or a customHeaderName if the standard name is set to OTHER. The headerValue serves as a match condition when the action is DELETE or MODIFY, and the newHeaderValue applies when the action is ADD or MODIFY.

Option	Type	Description	Requires
`action`	enum	Either `ADD`, `DELETE`, `MODIFY`, or `PASS` incoming HTTP request headers.		{"displayType":"enum","options":["ADD","DELETE","MODIFY","PASS"],"tag":"select"}
	`ADD`	Add the header.
	`DELETE`	Delete the header.
	`MODIFY`	Modify the header.
	`PASS`	Pass through the header.
`standardAddHeaderName`	enum	If the value of `action` is `ADD`, this specifies the name of the field to add.	`action` is `ADD`	{"displayType":"enum","options":["ACCEPT_ENCODING","ACCEPT_LANGUAGE","OTHER"],"tag":"select"} {"if":{"attribute":"action","op":"eq","value":"ADD"}}
	`ACCEPT_ENCODING`	Add an `Accept-Encoding` header.
	`ACCEPT_LANGUAGE`	Add an `Accept-Language` header.
	`OTHER`	Specify another header to add.
`standardDeleteHeaderName`	enum	If the value of `action` is `DELETE`, this specifies the name of the field to remove.	`action` is `DELETE`	{"displayType":"enum","options":["IF_MODIFIED_SINCE","VIA","OTHER"],"tag":"select"} {"if":{"attribute":"action","op":"eq","value":"DELETE"}}
	`IF_MODIFIED_SINCE`	The `If-Modified-Since` header.
	`VIA`	The `Via` header.
	`OTHER`	Specify another header to remove.
`standardModifyHeaderName`	enum	If the value of `action` is `MODIFY`, this specifies the name of the field to modify.	`action` is `MODIFY`	{"displayType":"enum","options":["ACCEPT_ENCODING","ACCEPT_LANGUAGE","OTHER"],"tag":"select"} {"if":{"attribute":"action","op":"eq","value":"MODIFY"}}
	`ACCEPT_ENCODING`	Add an `Accept-Encoding` header.
	`ACCEPT_LANGUAGE`	Add an `Accept-Language` header.
	`OTHER`	Specify another header to add.
`standardPassHeaderName`	enum	If the value of `action` is `PASS`, this specifies the name of the field to pass through.	`action` is `PASS`	{"displayType":"enum","options":["ACCEPT_ENCODING","ACCEPT_LANGUAGE","OTHER"],"tag":"select"} {"if":{"attribute":"action","op":"eq","value":"PASS"}}
	`ACCEPT_ENCODING`	Add an `Accept-Encoding` header.
	`ACCEPT_LANGUAGE`	Add an `Accept-Language` header.
	`OTHER`	Specify another header to add.
`customHeaderName`	string (allows variables)	Specifies a custom field name that applies when the relevant standard header name is set to `OTHER`.	`standardAddHeaderName` is `OTHER` OR `standardDeleteHeaderName` is `OTHER` OR `standardModifyHeaderName` is `OTHER` OR `standardPassHeaderName` is `OTHER`	{"displayType":"string","tag":"input","type":"text"} {"if":{"op":"or","params":[{"attribute":"standardAddHeaderName","op":"eq","value":"OTHER"},{"attribute":"standardDeleteHeaderName","op":"eq","value":"OTHER"},{"attribute":"standardModifyHeaderName","op":"eq","value":"OTHER"},{"attribute":"standardPassHeaderName","op":"eq","value":"OTHER"}]}}
`headerValue`	string (allows variables)	Specifies the new header value.	`action` is `ADD`	{"displayType":"string","tag":"input","type":"text"} {"if":{"attribute":"action","op":"eq","value":"ADD"}}
`newHeaderValue`	string (allows variables)	Supplies an HTTP header replacement value.	`action` is `MODIFY`	{"displayType":"string","tag":"input","type":"text"} {"if":{"attribute":"action","op":"eq","value":"MODIFY"}}
`avoidDuplicateHeaders`	boolean	When enabled with the `action` set to `MODIFY`, prevents creation of more than one instance of a header.	`action` is `MODIFY`	{"displayType":"boolean","tag":"input","type":"checkbox"} {"if":{"attribute":"action","op":"eq","value":"MODIFY"}}