HTTP Headers

Attribution-Reporting-Eligible header

HTTP Header

The HTTP Attribution-Reporting-Eligible request header signifies that the corresponding response is able to register an attribution source or trigger.

This header is never manually set; instead, it is sent by the browser in response to various HTML element or JavaScript request configurations. Based on the permitted registrations specified in the Attribution-Reporting-Eligible value, the server is expected to reply with either an Attribution-Reporting-Register-Source or Attribution-Reporting-Register-Trigger header to complete the registration of an attribution source or trigger, respectively.

For additional details, see the Attribution Reporting API.

Header type	Request header
Forbidden request header	No

Syntax

Attribution-Reporting-Eligible: <allowed-registrations>

Directives

<allowed-registrations>

A structured-header dictionary indicating the registrations permitted in the associated response. Possible keys include:

event-source: An event-based attribution source can be registered.
navigation-source: A navigation-based attribution source can be registered.
trigger: An attribution trigger can be registered.

Every response within a redirect chain can register a maximum of one source or one trigger.

Example

Attribution-Reporting-Eligible: trigger

How to Modify Header using Requestly

Requestly is a powerful Chrome extension that allows you to modify HTTP headers, including the Attribution-Reporting-Eligible header. This is useful when you want to test whether a request is eligible to register attribution sources or triggers as part of the Attribution Reporting API during development or debugging. Steps to Modify the Attribution-Reporting-Eligible Header:

Install and open the Requestly Chrome extension. You can find it on the Chrome Web Store.
Create a new rule: Click on “Create Rule” and choose “Modify Headers” from the list of available rule types.
Add a new header modification:
- Under “Action”, select “Add” or “Override”.
- In the “Header Name” field, enter Attribution-Reporting-Eligible.
- In the “Header Value” field, enter the appropriate eligibility value (for example, event-source or trigger).
Set the URL condition: Specify the URL or pattern where this header should apply (for example, https://your-website.com/*).
Save the rule.

Once configured, Requestly will inject the Attribution-Reporting-Eligible header into all matching requests. This allows you to simulate eligibility for registering attribution sources or triggers.

You might need to modify the Attribution-Reporting-Eligible header to test campaign attribution flows, validate conversion measurement logic, or debug Privacy Sandbox integrations without changing your live server configuration. This helps ensure attribution reporting works correctly before deployment.