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Scoped custom element registries #1027
Description
Description
Original proposal:
https://github.com/WICG/webcomponents/blob/gh-pages/proposals/Scoped-Custom-Element-Registries.md
More up to date:
whatwg/html#10854
This proposal allows for multiple custom element definitions for a single tag name to exist within a page.
This is accomplished by allowing user code to create multiple custom element registries and associate them with shadow roots that function as scopes for element creation and custom element definitions. Potentially custom elements created within a scope use the registry for that scope to perform upgrades. New element construction APIs are added to ShadowRoot to allow element creation to be associated with a scope.
Specification
https://html.spec.whatwg.org/multipage/custom-elements.html#custom-elements-api https://dom.spec.whatwg.org/#element-custom-element-registry
web-feature
https://web-platform-dx.github.io/web-features-explorer/features/scoped-custom-element-registries/
Test Links
https://github.com/web-platform-tests/wpt/tree/master/custom-elements/registries
Additional Signals
whatwg/html#10869
https://webkit.org/standards-positions/#:~:text=Scoped%20Custom%20Element%20Registries
mozilla/standards-positions#424
Activity
github-actions commentedon Sep 5, 2025
This comment was automatically generated based on the information you provided. Please don't edit it.
Below is additional information about the web feature (from the web-features project) which is referenced in your proposal.
If this doesn't accurately correspond to your proposal, please update your initial comment to include
web-features: <feature-id>.To find feature IDs, use the web-features explorer.
Feature Scoped custom element registries
CustomElementRegistry()constructor creates a new custom element registry that's separate from the globalwindow.customElementsregistry. Creating more than one registry is useful for multiple custom elements that have the same tag name to coexist.yulunwu2 commentedon Nov 21, 2025
https://wpt.fyi/results/custom-elements/registries?label=master&label=experimental&aligned&q=custom-elements%2Fregistries
dandclark commentedon Jan 28, 2026
Looking at the tests under https://wpt.fyi/results/custom-elements/registries, all are related to scoped custom elements registry except for these, which only deal with the global registry:
So a good test list would be https://wpt.fyi/results/custom-elements/registries excluding those 6 tests.
wpt-interop commentedon Feb 12, 2026
Thank you for proposing Scoped custom element registries for Interop 2026.
We are pleased to let you know that it has been accepted as part of the Scoped custom element registries focus area.
You’ll be able to track progress on this topic throughout the year via the Interop 2026 dashboard.
Posted on behalf of the Interop team.