Could you please request Debuggability and Testing bits in your
chromestatus entry
On 11/8/25 3:35 a.m., Nan Lin wrote:
Intent to Deprecate and Remove: Attribution Reporting API
Contact emails
[email protected] <mailto:[email protected]>, [email protected]
<mailto:[email protected]>, [email protected]
<mailto:[email protected]>
Explainer
https://github.com/WICG/attribution-reporting-api
<https://github.com/WICG/attribution-reporting-api>
Specification
https://wicg.github.io/attribution-reporting-api/
<https://wicg.github.io/attribution-reporting-api/>
Summary
The Attribution Reporting API (ARA) is a privacy-preserving web API
designed to measure ad conversions without third-party cookies or user
tracking across sites.
Following Chrome's announcement
<https://privacysandbox.com/news/privacy-sandbox-next-steps/>that the
current approach to third-party cookies will be maintained, we are now
planning to deprecate and remove
<https://privacysandbox.com/news/update-on-plans-for-privacy-sandbox-technologies/>the
Attribution Reporting API (along with certain other Privacy Sandbox
APIs, as outlined on the Privacy Sandbox feature status page
<https://privacysandbox.google.com/overview/status>).
Blink component
Internals > AttributionReporting
<https://bugs.chromium.org/p/chromium/issues/list?q=component:Internals%3EAttributionReporting>
Web Feature ID
None
Motivation
Chrome has announced
<https://privacysandbox.com/news/update-on-plans-for-privacy-sandbox-technologies/>that
the current approach to third-party cookies will be maintained. Given
this, we expect adoption of the Attribution Reporting API to decrease
over time, as cross-site measurement will remain possible in Chrome
using third-party cookies. Further, although Microsoft Edge integrates
with the Attribution Reporting API, most other browser engines have
not signaled interest in launching the API. Removing this (and certain
other Privacy Sandbox APIs
<https://privacysandbox.google.com/overview/status>) will help focus
efforts on the proposed interoperable Attribution
<https://github.com/w3c/attribution>standard.
Developer-facing impact
Sites that are using the Attribution Reporting API for conversion
measurement and do not migrate to alternative solutions may experience
a disruption in conversion measurement on eventual removal of the API
code from Chrome.
*
Conversion measurement disruption:All ad conversion events relying
on the deprecated API will fail to register or report. Sites using
this API as their primary or supplementary method for ad
measurement will lose visibility into campaign performance metrics
derived from this technology.
*
Public API surface:The following outlines the consequences of
deprecating and removing the Attribution Reporting API for each of
the interfaces defined here
<https://wicg.github.io/attribution-reporting-api/#idl-index>.
o
Potentially user-breaking
+
XMLHttpRequest.setAttributionReporting(): Calling
setAttributionReporting()on an XMLHttpRequestobject will
throw an exception because the method will no longer
exist. This is a breaking change for any site that calls
this method. Given that this feature is not implemented in
other browsers, it is likely that sites are already using
feature detection to check the method’s existence before
calling it, which would prevent breakage. We will start to
track the usage of this method.
o
Non user-breaking
+
HTMLAttributionSrcElementUtilsand the
attributionsrcattribute: The attributionsrcattribute on
<a>, <area>, <img>, and <script> elements will be ignored.
Any values assigned to this attribute will have no effect,
and the browser will no longer initiate background
requests to register attribution sources/triggers.
Additionally we will no longer process trigger headers on
legacy subresource requests that lack the opt-in (either
on an element or fetch/XHR). This will not cause any
visible breakage or errors on the page for the user, but
it will silently prevent conversion measurement for sites
that rely on this attribute.
+
attributionsrcin window.open(): The attributionsrcfeature
in the featuresstring of a window.open()call will be
ignored. The window will still open as requested, but no
attribution source will be registered. This will not cause
any visible breakage or errors on the pages for the user,
but it will silently prevent conversion measurement for
sites that rely on this functionality.
+
AttributionReportingRequestOptionsand the
attributionReportingmember in RequestInit: The
attributionReportingproperty within the options of a
fetch() call will be ignored. The fetch request will still
be made, but it will not trigger any attribution-related
functionality. This change will not cause any JavaScript
errors, but conversion measurement that relies on the
fetch requests will no longer work.
+
Attribution-Reporting-Eligibleand
Attribution-Reporting-Supportheaders: Since the browser
will no longer process the attributionsrcattribute or the
attributionReportingproperty in requests, it will no
longer send these two headers on outgoing requests.
+
attribution-reportingpermission policy:
Theattribution-reportingpermission policy
<https://wicg.github.io/attribution-reporting-api/#permission-policy-integration>will
be removed along with the API. Since the API it controls
will no longer exist, the permission policy will have no
effect and its removal is not considered a breaking change.
Planning and Estimated Milestones
Deprecate the browser API surface in M144 and remove in M150.
There will be one aspect of ARA that will end sooner. Server-side
summary report computation will no longer operate by late December
2025. We have already communicated to the users of that service of
these plans. Such users can use debug reports instead until the
removal of the ARA surface as a whole. Since this impacts post-facto
server-side operations, it will not incur any user-facing breakage.
Currently ~20%
<https://chromestatus.com/metrics/webfeature/timeline/popularity/282>of
page loads use the Attribution Reporting API. While ARA’s usage as a
percentage of page loads is quite high, it is driven by a small number
of third-party ad tech scripts present on a large number of sites. We
will continue to monitor usage in addition to providing comprehensive
updates on privacysandbox.google.com
<https://privacysandbox.google.com/>with the status of the API and
deprecation plans <https://privacysandbox.google.com/overview/status>.
We will proactively work toward reducing ARA usage to low levels once
this intent is approved, including disallowing any new enrollment
sign-ups, and contacting enrolled sites to inform them about the
deprecation timelines.
Link to entry on the Chrome Platform Status
https://chromestatus.com/feature/6320639375966208
<https://chromestatus.com/feature/6320639375966208>
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