LGTM3 to deprecate.
On 11/13/25 1:44 a.m., Daniel Bratell wrote:
LGTM2 for deprecation (not for the actual removal)
/Daniel
On 2025-11-12 17:28, Vladimir Levin wrote:
LGTM1 to deprecate. This feature removal sounds riskier than other
related features, especially coupled with 20% page loads. So although
the plan to monitor for 6 milestones sounds good, this approval does
*not* extend to removal. Please come back to this thread closer to
the proposed removal to see if the usage had dropped substantially.
On Sunday, November 9, 2025 at 7:47:04 PM UTC-5 Mike Taylor wrote:
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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