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Create a request header transform rule v…

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Create a request header transform rule via API

Last updated May 5, 2026|Copy as Markdown|View as Markdown|Agent setup

OverviewBasic rule settingsProcedureExample requestsRequired API token permissions

Use the Rulesets API to create Request Header Transform Rules via API. Refer to the Rules examples gallery for common use cases.

If you are using Terraform, refer to Transform Rules configuration using Terraform.

Basic rule settings

When creating a request header transform rule via API, make sure you:

Set the rule action to rewrite.

Define the header modification parameters in the action_parameters field according to the operation to perform (set or remove header).

Deploy the rule to the http_request_late_transform phase at the zone level.

Procedure

Follow this workflow to create a request header transform rule for a given zone via API:

Use the List zone rulesets operation to check if there is already a ruleset for the http_request_late_transform phase at the zone level.

If the phase ruleset does not exist, create it using the Create a zone ruleset operation. In the new ruleset properties, set the following values:

kind: zone

phase: http_request_late_transform

Use the Update a zone ruleset operation to add a request header transform rule to the list of ruleset rules. Alternatively, include the rule in the Create a zone ruleset request mentioned in the previous step.

Make sure your API token has the required permissions to perform the API operations.

Example requests

Example: Add an HTTP request header with a static value

The following example sets the rules of an existing phase ruleset ($RULESET_ID) to a single request header transform rule — adding an HTTP request header with a static value — using the Update a zone ruleset operation. The response will contain the complete definition of the ruleset you updated.

Required API token permissions
At least one of the following token permissions is required:
Response Compression Write

Config Settings Write

Dynamic URL Redirects Write

Cache Settings Write

Custom Errors Write

Origin Write

Managed headers Write

Zone Transform Rules Write

Mass URL Redirects Write

Magic Firewall Write

L4 DDoS Managed Ruleset Write

HTTP DDoS Managed Ruleset Write

Sanitize Write

Transform Rules Write

Select Configuration Write

Bot Management Write

Zone WAF Write

Account WAF Write

Account Rulesets Write

Logs Write

Logs Write
Update a zone rulesetbashcurl "https://api.cloudflare.com/client/v4/zones/$ZONE_ID/rulesets/$RULESET_ID" \ --request PUT \ --header "Authorization: Bearer $CLOUDFLARE_API_TOKEN" \ --json '{ "rules": [ { "ref": "add_header_source", "expression": "(starts_with(http.request.uri.path, \"/en/\"))", "description": "My first request header transform rule", "action": "rewrite", "action_parameters": { "headers": { "X-Source": { "operation": "set", "value": "Cloudflare" } } } } ] }'{ "result": { "id": "<RULESET_ID>", "name": "Zone-level Late Transform Ruleset", "description": "Zone-level ruleset that will execute Late Transform Rules.", "kind": "zone", "version": "2", "rules": [ { "ref": "add_header_source", "id": "<RULE_ID>", "version": "1", "action": "rewrite", "action_parameters": { "headers": { "X-Source": { "operation": "set", "value": "Cloudflare" } } }, "expression": "(starts_with(http.request.uri.path, \"/en/\"))", "description": "My first request header transform rule", "last_updated": "2021-04-14T14:42:04.219025Z", "ref": "<RULE_REF>" } ], "last_updated": "2021-04-14T14:42:04.219025Z", "phase": "http_request_late_transform" }, "success": true, "errors": [], "messages": []}
Use the ref field to get stable rule IDs across updates when using Terraform. Adding this field prevents Terraform from recreating the rule on changes. For more information, refer to Troubleshooting in the Terraform documentation.

Example: Add an HTTP request header with a dynamic value

The following example sets the rules of an existing phase ruleset ($RULESET_ID) to a single request header transform rule — adding an HTTP request header with a dynamic value — using the Update a zone ruleset operation. The response will contain the complete definition of the ruleset you updated.

Required API token permissions
At least one of the following token permissions is required:
Response Compression Write

Config Settings Write

Dynamic URL Redirects Write

Cache Settings Write

Custom Errors Write

Origin Write

Managed headers Write

Zone Transform Rules Write

Mass URL Redirects Write

Magic Firewall Write

L4 DDoS Managed Ruleset Write

HTTP DDoS Managed Ruleset Write

Sanitize Write

Transform Rules Write

Select Configuration Write

Bot Management Write

Zone WAF Write

Account WAF Write

Account Rulesets Write

Logs Write

Logs Write
Update a zone rulesetbashcurl "https://api.cloudflare.com/client/v4/zones/$ZONE_ID/rulesets/$RULESET_ID" \ --request PUT \ --header "Authorization: Bearer $CLOUDFLARE_API_TOKEN" \ --json '{ "rules": [ { "ref": "add_header_bot_score", "expression": "(starts_with(http.request.uri.path, \"/en/\"))", "description": "My first request header transform rule", "action": "rewrite", "action_parameters": { "headers": { "X-Bot-Score": { "operation": "set", "expression": "to_string(cf.bot_management.score)" } } } } ] }'{ "result": { "id": "<RULESET_ID>", "name": "Zone-level Late Transform Ruleset", "description": "Zone-level ruleset that will execute Late Transform Rules.", "kind": "zone", "version": "2", "rules": [ { "ref": "add_header_bot_score", "id": "<RULE_ID>", "version": "1", "action": "rewrite", "action_parameters": { "headers": { "X-Bot-Score": { "operation": "set", "expression": "to_string(cf.bot_management.score)" } } }, "expression": "(starts_with(http.request.uri.path, \"/en/\"))", "description": "My first request header transform rule", "last_updated": "2021-04-14T14:42:04.219025Z", "ref": "<RULE_REF>" } ], "last_updated": "2021-04-14T14:42:04.219025Z", "phase": "http_request_late_transform" }, "success": true, "errors": [], "messages": []}
Use the ref field to get stable rule IDs across updates when using Terraform. Adding this field prevents Terraform from recreating the rule on changes. For more information, refer to Troubleshooting in the Terraform documentation.

Example: Remove an HTTP request header

The following example sets the rules of an existing phase ruleset ($RULESET_ID) to a single request header transform rule — removing an HTTP request header — using the Update a zone ruleset. The response will contain the complete definition of the ruleset you updated.

Required API token permissions
At least one of the following token permissions is required:
Response Compression Write

Config Settings Write

Dynamic URL Redirects Write

Cache Settings Write

Custom Errors Write

Origin Write

Managed headers Write

Zone Transform Rules Write

Mass URL Redirects Write

Magic Firewall Write

L4 DDoS Managed Ruleset Write

HTTP DDoS Managed Ruleset Write

Sanitize Write

Transform Rules Write

Select Configuration Write

Bot Management Write

Zone WAF Write

Account WAF Write

Account Rulesets Write

Logs Write

Logs Write
Update a zone rulesetbashcurl "https://api.cloudflare.com/client/v4/zones/$ZONE_ID/rulesets/$RULESET_ID" \ --request PUT \ --header "Authorization: Bearer $CLOUDFLARE_API_TOKEN" \ --json '{ "rules": [ { "ref": "remove_header_cf_connecting_ip", "expression": "(starts_with(http.request.uri.path, \"/en/\"))",
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