Note. For polyfills that work with the older Custom Elements and Shadow DOM v0 specs, see the v0 branch of the webcomponentsjs repo.

Note. For polyfills that work with HTML Imports, see the v1 branch of the webcomponentsjs repo.

A suite of polyfills supporting the Web Components specs:

• Custom Elements v1: allows authors to define their own custom tags (spec, tutorial, polyfill).
• Shadow DOM v1: provides encapsulation by hiding DOM subtrees under shadow roots (spec, tutorial, shadydom polyfill, shadycss polyfill).

For browsers that need it, there are also some minor polyfills included:

• HTMLTemplateElement
• Promise
• Event, CustomEvent, MouseEvent constructors and Object.assign, Array.from (see webcomponentsjs)
• URL constructor

The entire WebComponents suite can be installed at once and loaded together for maximum compatibility.

More information about how the polyfill bundles, and feature-detecting loader work are in the webcomponentsjs README.

Individual polyfills can be installed with the @webcomponentsjs/ scope

npm install @webcomponents/custom-elements

Note: This polyfill requires manual setup and API calls for style encapsulation

npm install @webcomponents/shadydom @webcomponents/shadycss

npm install @webcomponents/template

⚠️ HTML Imports has been deprecated, and will be removed from Chrome in the future. Please transition to ES Modules! ⚠️

npm install @webcomponents/html-imports

npm install
npm run bootstrap
npm run build

npm run build
npm test