HTTP Response Header Modification Rules

You can manipulate the headers included in the HTTP response through HTTP Response Header Modification Rules. Through these rules you can:

• Set the value of an HTTP response header to a literal string value, overwriting its previous value or adding a new header to the response.
• Set the value of an HTTP response header according to an expression, overwriting its previous value or adding a new header to the response.
• Remove an HTTP header from the response.

You can create an HTTP Response Header Modification Rule in the dashboard or via API.

To modify HTTP headers in the request, refer to HTTP Request Header Modification Rules.

​​ Important remarks

• The response header values are calculated using the field values from the corresponding HTTP request. For example, the value of ip.src.country will be the country of the website visitor, not the origin where the response was sent from.

• You cannot modify or remove HTTP response headers whose name starts with cf- or x-cf-.

• You cannot modify the value of certain headers such as server, eh-cache-tag, or eh-cdn-cache-control.

• Currently you cannot reference IP Lists in expressions of HTTP Response Header Modification Rules.

• The HTTP response header removal operation will remove all response headers with the provided name.

• If you modify the value of an existing HTTP response header using an expression that evaluates to an empty string ("") or an undefined value, the HTTP response header is removed.

• Currently, there is a limited number of HTTP response headers that you cannot modify. Cloudflare may remove restrictions for some of these HTTP response headers when presented with valid use cases. Create a post in the community Open external link for consideration.

• Any response header modifications will also apply to Cloudflare error pages and custom error pages Open external link .