Custom fields

import { APIRequest, DashButton } from "~/components";

The HTTP requests dataset includes most standard log information by default. However, if you need to capture additional request or response headers or cookies, you can use custom fields to tailor the logs to your specific needs

Custom fields are configured per zone. They apply to all HTTP requests Logpush jobs that process the zone, including account-scoped jobs. The job must include the request headers, response headers, or cookie fields. You can log these fields in their raw form or as transformed values.

Account-scoped jobs honor the custom fields configuration for each zone. You cannot configure custom fields once for every zone in an account.

:::note[By default:]

• Request headers are logged as raw values.
• Response headers are logged as transformed values. :::

This default behavior can be changed. You can configure either request or response headers to be logged as raw or transformed, depending on your needs - but not both for the same header.

Custom fields can be enabled via API or the Cloudflare dashboard.

:::note Custom fields are only available for the HTTP requests dataset. They apply to account-scoped and zone-scoped jobs. :::

:::note There is no way to automatically forward all custom headers in Logpush without manually specifying each one. Each request or response header must be individually configured using Custom Fields. :::

Enable custom rules via API

Use the Rulesets API to create a rule that configures custom fields. For more information on concepts like phases, rulesets, and rules, as well as the available API operations, refer to the Ruleset Engine documentation.

To configure custom fields:

1. Create a rule to configure the list of custom fields.
2. Include the Cookies, RequestHeaders, and/or ResponseHeaders fields in your Logpush job.

1. Create a rule to configure the list of custom fields

Create a rule configuring the list of custom fields in the http_log_custom_fields phase at the zone level. Set the rule action to log_custom_field and the rule expression to true.

The action_parameters object that you must include in the rule that configures the list of custom fields should have the following structure:

"action_parameters": {
//select raw (default) or transformed request header
  "request_fields": [
    { "name": "<http_request_header_raw>" }
  ],
  "transformed_request_fields": [
    { "name": "<http_request_header_transformed>" }
  ],
//select raw or transformed (default) response header
  "response_fields": [
    { "name": "<http_response_header_transformed>" }
  ],
  "raw_response_fields": [
    { "name": "<http_response_header_raw>" }
  ],
  "cookie_fields": [
    { "name": "<cookie_name>" }
  ]
}

Ensure that your rule definition complies with the following:

• You must include at least one of the following arrays in the action_parameters object: request_fields, transformed_request_fields, response_fields, raw_response_fields, and cookie_fields.
• You must enter HTTP request and response header names in lower case.
• Cookie names are case sensitive — you must enter cookie names with the same capitalization they have in the HTTP request.
• You must set the rule expression to true.
• You can only log raw or transformed values for either request or response headers but not both for the same header.

Perform the following steps to create the rule:

1. Use the List zone rulesets operation to check if there is already an entry point ruleset for the http_log_custom_fields phase at the zone level (you can only have one entry point ruleset per phase):

   If there is an entry point ruleset for the http_log_custom_fields phase (that is, a ruleset with "kind": "zone" and "phase": "http_log_custom_fields"), take note of the ruleset ID.

2. (Optional) If the response did not include a ruleset with "kind": "zone" and "phase": "http_log_custom_fields", create the phase entry point ruleset using the Create a zone ruleset operation:

   <APIRequest path="/zones/{zone_id}/rulesets" method="POST" json={{ name: "Zone-level phase entry point", kind: "zone", description: "This ruleset configures custom log fields.", phase: "http_log_custom_fields", }} roles={false} />

   Take note of the ruleset ID included in the response.

3. Use the Update a zone ruleset operation to define the rules of the entry point ruleset you found (or created in the previous step), adding a rule with the custom fields configuration. The rules you include in the request will replace all the rules in the ruleset.

   The following example configures custom fields with the names of the HTTP request headers, HTTP response headers, and cookies you wish to include in Logpush logs:

   <APIRequest path="/zones/{zone_id}/rulesets/{ruleset_id}" method="PUT" json={{ rules: [ { action: "log_custom_field", expression: "true", description: "Set Logpush custom fields for HTTP requests", action_parameters: { request_fields: [ { name: "content-type" }, { name: "x-forwarded-for" }, ], transformed_request_fields: [{ name: "host" }], response_fields: [{ name: "server" }, { name: "content-type" }], raw_response_fields: [{ name: "allow" }], cookie_fields: [ { name: "__ga" }, { name: "accountNumber" }, { name: "__cfruid" }, ], }, }, ], }} roles={false} />

   {
   	"result": {
   		"id": "<RULESET_ID>",
   		"name": "Zone-level phase entry point",
   		"description": "This ruleset configures custom log fields.",
   		"kind": "zone",
   		"version": "2",
   		"rules": [
   			{
   				"id": "<RULE_ID_1>",
   				"version": "1",
   				"action": "log_custom_field",
   				"action_parameters": {
   					"request_fields": [
   						{ "name": "content-type" },
   						{ "name": "x-forwarded-for" }
   					],
   					"transformed_request_fields": [{ "name": "host" }],
   					"response_fields": [
   						{ "name": "server" },
   						{ "name": "content-type" }
   					],
   					"raw_response_fields": [{ "name": "allow" }],
   					"cookie_fields": [
   						{ "name": "__ga" },
   						{ "name": "accountNumber" },
   						{ "name": "__cfruid" }
   					]
   				},
   				"expression": "true",
   				"description": "Set Logpush custom fields for HTTP requests",
   				"last_updated": "2021-11-21T11:02:08.769537Z",
   				"ref": "<RULE_REF_1>",
   				"enabled": true
   			}
   		],
   		"last_updated": "2021-11-21T11:02:08.769537Z",
   		"phase": "http_log_custom_fields"
   	},
   	"success": true,
   	"errors": [],
   	"messages": []
   }
   

Record duplicate response header values

Some headers sent from the origin — such as set-cookie — may have multiple values that you want to capture. You can use the Rulesets API to specify which headers should have all their values logged.

<APIRequest path="/zones/{zone_id}/rulesets/{ruleset_id}" method="PUT" json={{ rules: [ { action: "log_custom_field", expression: "true", description: "Set Logpush custom fields for HTTP requests", action_parameters: { response_fields: [{ name: "set-cookie", preserve_duplicates: true }], }, }, ], }} roles={false} />

Note that preserve_duplicates applies to both response_fields and raw_response_fields. If there are no transform rules that affect a header, including preserve_duplicates in either response_fields or raw_response_fields should achieve the same result.

In this example, all values of the set-cookie headers will be logged. They will appear as an array of string values under ResponseFields, for example:

{
  // ...
  "ResponseFields": {
    "set-cookie": ["name1=val1", "name2=val2", ...]
  }
}

You can use a worker or custom logic at your logpush destination to extract these values.

2. Include the custom fields in your Logpush job

Next, include Cookies, RequestHeaders, ResponseHeaders, and/or ResponseFields, depending on your custom field configuration, in the list of fields of the output_options job parameter when creating or updating a job. The logs will contain the configured custom fields and their values in the request/response.

For example, consider the following request that creates a job that includes custom fields:

<APIRequest path="/zones/{zone_id}/logpush/jobs" method="POST" json={{ name: "<DOMAIN_NAME>", destination_conf: "s3://<BUCKET_PATH>?region=us-west-2", dataset: "http_requests", output_options: { field_names: [ "RayID", "EdgeStartTimestamp", "Cookies", "RequestHeaders", "ResponseHeaders", ], timestamp_format: "rfc3339", }, ownership_challenge: "<OWNERSHIP_CHALLENGE_TOKEN>", }} />

:::note[Note for Cloudflare Access users]

If you are a Cloudflare Access user, as of March 2022 you have to manually add the cf-access-user user identity header to your logs by creating a custom fields ruleset or adding the cf-access-user HTTP request header to your custom fields configuration. Additionally, make sure that you include the RequestHeaders field in your Logpush job.

:::

Enable custom fields via dashboard

1. In the Cloudflare dashboard, select your account and zone. Then go to Observability > Export > Logpush.

2. Select the Configuration tab.

3. In the Custom log fields section, select Edit Custom Fields.

4. Select Set new Custom Field.

5. From the Field Type dropdown, select Request Header, Response Header, or Cookies and type the Field Name.

6. When you are done, select Save.

Use case: Logging mTLS certificate headers

To log mTLS certificate details (such as cf-cert-subject-dn or cf-cert-issuer-dn) in Logpush, you need to:

1. Enable the Add TLS client auth headers Managed Transform to inject the certificate headers.
2. Configure Logpush custom fields using transformed_request_fields (not request_fields) to capture these Cloudflare-injected headers.
3. Ensure your Logpush job includes the RequestHeaders field.

The mTLS headers are injected by Cloudflare after the client request is received, so they must be captured using transformed_request_fields rather than request_fields.

For more information on configuring client certificates, refer to mTLS authentication.

Limitations

• Custom fields allow 100 headers per field type — this applies separately to request_fields, transformed_request_fields, response_fields, raw_response_fields, and cookie_fields.
• The request header Range is currently not supported by Custom Fields.
• Transformed and raw values for request and response headers are available only via the API and cannot be set through the UI.