Thanks.
On 6/17/26 6:26 a.m., Felipe Erias wrote:
Hi Mike,
We debated in the CL whether to use a PSA or an Intent to Ship. You
are right that this is a new feature in Chromium, so I will re-submit
it as an Intent to Ship.
Best,
Felipe
On Thursday, 11 June 2026 at 17:52:13 UTC+2 [email protected] wrote:
This seems like this should be an Intent to Ship, as you're adding
support for a few feature. Is there any reason you chose PSA?
On 6/10/26 12:17 p.m., Chromestatus wrote:
*Contact emails*
[email protected]
*Specification*
https://html.spec.whatwg.org/#attr-template-shadowrootslotassignment
*Summary*
Adds the shadowrootslotassignment attribute to the <template>
element, allowing declarative shadow roots to use manual slot
assignment. Until now this option was only available
imperatively, via attachShadow({slotAssignment: "manual"}), so
components that rely on manual assignment could not create their
shadow roots declaratively. The attribute accepts "named" (the
default, preserving current behavior) and "manual", and is
reflected by the shadowRootSlotAssignment property on
HTMLTemplateElement.
*Blink component*
Blink>DOM>ShadowDOM
<https://issues.chromium.org/issues?q=customfield1222907:%22Blink%3EDOM%3EShadowDOM%22>
*Web Feature ID*
declarative-shadow-dom
<https://webstatus.dev/features/declarative-shadow-dom>
*Risks*
*Interoperability and Compatibility*
Low risk. The new behavior is opt-in: it only applies when a page
explicitly sets shadowrootslotassignment="manual", and the
default ("named") matches current behavior, so existing content
is unaffected. The attribute is specified in the HTML Standard
(merged via https://github.com/whatwg/html/pull/12267, originally
raised in https://github.com/WICG/webcomponents/issues/967) and
both Gecko and WebKit have already implemented it, so shipping in
Chromium completes cross-engine support. The change is guarded by
the ShadowRootSlotAssignment feature flag (enabled by default
from M151), retained as a kill switch and expected to be removed
around M153.
/Gecko/:
Shipped/Shipping (https://bugzilla.mozilla.org/show_bug.cgi?id=2023824)
/WebKit/:
Shipped/Shipping (https://bugs.webkit.org/show_bug.cgi?id=310090)
https://github.com/WebKit/standards-positions/issues/631
/Web developers/:
Positive (https://github.com/WICG/webcomponents/issues/967)
/Other signals/:
*WebView application risks*
Does this intent deprecate or change behavior of existing APIs,
such that it has potentially high risk for Android WebView-based
applications?
/No information provided/
*Debuggability*
No new DevTools work required. The attribute is visible in the
Elements panel like the other shadowroot* attributes, and the
resulting shadow root's mode is already exposed via
ShadowRoot.slotAssignment.
*Will this feature be supported on all six Blink platforms
(Windows, Mac, Linux, ChromeOS, Android, and Android WebView)?*
Yes
*Is this feature fully tested by web-platform-tests
<https://chromium.googlesource.com/chromium/src/+/main/docs/testing/web_platform_tests.md>?*
Yes
https://wpt.fyi/results/shadow-dom/declarative/declarative-shadow-dom-repeats-slot-assignment.html
https://wpt.fyi/results/shadow-dom/declarative/declarative-shadow-dom-slot-assignment.html
https://wpt.fyi/results/shadow-dom/declarative/declarative-shadow-dom-slot-assignment-serialization.html
*Tracking bug*
https://issues.chromium.org/issues/493315747
*Estimated milestones*
Shipping on desktop 151
Shipping on Android 151
Shipping on WebView 151
*Link to entry on the Chrome Platform Status*
https://chromestatus.com/feature/5203283359694848
This intent message was generated by Chrome Platform Status
<https://chromestatus.com>.
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