webcomponents/polyfills

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Web Components Polyfills

Stars: 1.2k
Forks: 168
Open beginner issues: 0
Indexed issues: 94

Dominant language: HTML
License: BSD-3-Clause
Last GitHub push: Feb 23, 2026
Latest indexed: Sep 15, 2026
Contributing guide: Contributing guide
Code of conduct: No code of conduct
Beginner labels: No beginner labels indexed
PR merge metrics: No merged PRs in 30d

Open All

94 open issues indexed

[ShadyCSS] Cannot load the polyfill async Open

Package: shadycss Severity: Low Type: Bug wontfix

webcomponents/polyfills#33 · 3 comments · 0 reactions · 0 assignees · Indexed Sep 15, 2026
[Custom Elements] `instanceof Function` doesn't work for functions from other realms. Open

Package: custom-elements Severity: Medium Type: Bug

webcomponents/polyfills#105 · 11 comments · 0 reactions · 0 assignees · Indexed Sep 15, 2026
[Custom Elements] Custom element not "recognized" when added with Element.outerHTML Open

Package: custom-elements Severity: Medium Type: Feature wontfix

webcomponents/polyfills#106 · 5 comments · 0 reactions · 0 assignees · Indexed Sep 15, 2026
Missing DocumentOrShadowRoot interface implementation Open

webcomponents/polyfills#66 · 15 comments · 0 reactions · 1 assignee · Indexed Sep 15, 2026
[ShadyCSS] Curlies in styles break the preprocessor Open

Package: shadycss Severity: Low Type: Bug wontfix

webcomponents/polyfills#28 · 4 comments · 0 reactions · 1 assignee · Indexed Sep 15, 2026
[Custom Elements] Callback ordering is incorrect for `Node.prototype.replaceChild`. Open

Package: custom-elements Severity: Low Type: Bug wontfix

webcomponents/polyfills#107 · 4 comments · 0 reactions · 0 assignees · Indexed Sep 15, 2026
[ShadyCSS] Expose prepareTemplate for non template DocumentFragments Open

Package: shadycss Severity: Medium Type: Feature wontfix

webcomponents/polyfills#26 · 4 comments · 0 reactions · 0 assignees · Indexed Sep 15, 2026
[Custom Elements] Error in IE11: The custom element being constructed was not registered with `customElements`. Open

Package: custom-elements Severity: Medium Type: Bug wontfix

webcomponents/polyfills#108 · 11 comments · 1 reaction · 0 assignees · Indexed Sep 15, 2026
[ShadyCSS] Too specific slotted(*) causes unexpected styling Open

Package: shadycss Severity: Medium Type: Bug wontfix

webcomponents/polyfills#24 · 3 comments · 0 reactions · 0 assignees · Indexed Sep 15, 2026
[ShadyCSS] Selectors for slot element does not work Open

Package: shadycss Severity: Low Type: Feature wontfix

webcomponents/polyfills#22 · 2 comments · 0 reactions · 0 assignees · Indexed Sep 15, 2026
[ShadyCSS] Specificity issue when mixing straight and module-style CSS Open

Package: shadycss Severity: Medium Type: Bug wontfix

webcomponents/polyfills#23 · 4 comments · 0 reactions · 0 assignees · Indexed Sep 15, 2026
[ShadyCSS] error scoping distributed content Open

Package: shadycss Severity: High Type: Bug wontfix

webcomponents/polyfills#20 · 2 comments · 0 reactions · 0 assignees · Indexed Sep 15, 2026
[ShadyDOM] Shadow DOM is not scoped and elements doesn't get `style-scope` when template is cloned after CE definition Open

Package: shadycss Package: shadydom Severity: Medium Type: Bug wontfix

webcomponents/polyfills#77 · 4 comments · 3 reactions · 0 assignees · Indexed Sep 15, 2026
[ShadyDOM] Mutation Observer callback is not called for shadow hosts Open

Focus Area: Standards & Polyfills Package: shadydom Severity: High Type: Bug wontfix

webcomponents/polyfills#81 · 4 comments · 2 reactions · 0 assignees · Indexed Sep 15, 2026
[ShadyCSS] Integration with Lit/HyperHtml - Dynamic Class Interpolation Open

Package: shadycss Severity: Medium Type: Feature wontfix

webcomponents/polyfills#18 · 3 comments · 0 reactions · 0 assignees · Indexed Sep 15, 2026
[Custom Elements] Calling `setAttribute` with a non-lower cased attribute name does not trigger `attributeChangedCallback` Open

Severity: Medium Type: Bug wontfix

webcomponents/polyfills#110 · 4 comments · 2 reactions · 1 assignee · Indexed Sep 15, 2026
[ShadyCSS] How do we clean up? Open

Package: shadycss Severity: Medium Type: Feature wontfix

webcomponents/polyfills#15 · 3 comments · 0 reactions · 0 assignees · Indexed Sep 15, 2026
[WCJS] Remove `:unresolved` pseudo selector support Open

Package: webcomponentsjs Severity: Medium Type: Feature wontfix

webcomponents/polyfills#60 · 3 comments · 0 reactions · 0 assignees · Indexed Sep 15, 2026
[ShadyCSS] :host() selector containing multiple elements extremely slow when first element has a long name Open

More Info Needed Package: shadycss wontfix

webcomponents/polyfills#13 · 2 comments · 0 reactions · 0 assignees · Indexed Sep 15, 2026
[ShadyCSS] Provide option to add custom classname for scoping Open

Package: shadycss Severity: Low Type: Feature wontfix

webcomponents/polyfills#12 · 4 comments · 0 reactions · 0 assignees · Indexed Sep 15, 2026
[ShadyDOM] Add a way update insertion points when `preferPerformance` is set to true Open

Package: shadydom Severity: Medium Type: Feature wontfix

webcomponents/polyfills#92 · 2 comments · 0 reactions · 1 assignee · Indexed Sep 15, 2026
[ShadyDOM] HTMLElement ids don't get scoped Open

Package: shadydom Severity: Medium Type: Feature wontfix

webcomponents/polyfills#47 · 4 comments · 1 reaction · 0 assignees · Indexed Sep 15, 2026
[ShadyDOM] dispatchEvent on ShadowRoot throws an exception Open

Package: shadydom Severity: High Type: Bug wontfix

webcomponents/polyfills#93 · 2 comments · 0 reactions · 1 assignee · Indexed Sep 15, 2026
[ShadyDOM] Events dispatched by Light DOM children in connectedCallback cannot be handled Open

Package: shadydom Severity: High Type: Bug wontfix

webcomponents/polyfills#94 · 4 comments · 0 reactions · 0 assignees · Indexed Sep 15, 2026
[ShadyDOM] Edge slots not working if created with uppercase name Open

Package: shadydom Severity: Medium Type: Bug wontfix

webcomponents/polyfills#97 · 2 comments · 0 reactions · 0 assignees · Indexed Sep 15, 2026
[ShadyDOM] IE 11 Object doesn't support property or method 'assignedElements' Open

Package: shadydom Severity: Medium Type: Feature wontfix

webcomponents/polyfills#46 · 6 comments · 7 reactions · 1 assignee · Indexed Sep 15, 2026
[ShadyDOM] Shady DOM breaks angular router in Edge Open

Package: shadydom Severity: High Type: Bug wontfix

webcomponents/polyfills#98 · 3 comments · 0 reactions · 0 assignees · Indexed Sep 15, 2026
[ShadyDOM] Polymer.dom(parent).insertBefore(nodeToInsert, refNode) deletes node created by pressing enter key Open

Package: shadydom Severity: Medium Type: Bug wontfix

webcomponents/polyfills#101 · 3 comments · 0 reactions · 0 assignees · Indexed Sep 15, 2026
[Custom Elements] Finish port of some Custom Elements PRs Open

Severity: Medium Type: Feature wontfix

webcomponents/polyfills#138 · 6 comments · 1 reaction · 1 assignee · Indexed Sep 15, 2026
Multiple calls to `prepareTemplate` don't cascade as expected. Open

Package: shadycss wontfix

webcomponents/polyfills#156 · 2 comments · 0 reactions · 0 assignees · Indexed Sep 15, 2026
Implement FormData event Open

Epic Focus Area: Standards & Polyfills Severity: Medium Type: Feature

webcomponents/polyfills#172 · 11 comments · 9 reactions · 1 assignee · Indexed Sep 15, 2026
shadydom css of one component leaks in other components in Edge18 Open

Package: shadycss Package: shadydom Type: Bug wontfix

webcomponents/polyfills#184 · 3 comments · 0 reactions · 0 assignees · Indexed Sep 15, 2026
pollyfill seems to alter jQuery on MSIE11 Open

Focus Area: Standards & Polyfills More Info Needed Type: Bug wontfix

webcomponents/polyfills#198 · 3 comments · 2 reactions · 0 assignees · Indexed Sep 15, 2026
gecko 48 dispatch 'focus' event but intercept by polyfill Open

More Info Needed wontfix

webcomponents/polyfills#227 · 3 comments · 0 reactions · 0 assignees · Indexed Sep 15, 2026
[ShadyDOM] Allow use of `noPatch` modes without re-ordering polyfills Open

Focus Area: Standards & Polyfills Package: shadydom Type: Bug wontfix

webcomponents/polyfills#237 · 2 comments · 5 reactions · 0 assignees · Indexed Sep 15, 2026
[URL] URL polyfill isn't compatible with the spec: doesn't throw on partial URLs Open

Package: url Type: Feature wontfix

webcomponents/polyfills#241 · 6 comments · 2 reactions · 0 assignees · Indexed Sep 15, 2026
_element property on Custom Components breaks CSS Custom Properties Open

Focus Area: Standards & Polyfills Type: Bug wontfix

webcomponents/polyfills#245 · 3 comments · 0 reactions · 0 assignees · Indexed Sep 15, 2026
Setting ShadyDOM settings via `ShadyDOM` object and URL flags are incompatible. Open

Focus Area: Standards & Polyfills Package: shadydom Type: Bug wontfix

webcomponents/polyfills#250 · 2 comments · 0 reactions · 1 assignee · Indexed Sep 15, 2026
[WCJS] document.write does not work when webcomponents-loader.js is loaded asynchronously Open

Package: webcomponentsjs Severity: Low Type: Bug wontfix

webcomponents/polyfills#251 · 5 comments · 0 reactions · 0 assignees · Indexed Sep 15, 2026
[ShadyCSS] App loading performance issue in Chrome <= 45 Open

Focus Area: Standards & Polyfills Package: shadycss Severity: Low Type: Maintenance wontfix

webcomponents/polyfills#257 · 2 comments · 0 reactions · 0 assignees · Indexed Sep 15, 2026
failing shadycss scoping-api and disable-runtime tests Open

Focus Area: Standards & Polyfills Package: shadycss Severity: Medium Type: Bug wontfix

webcomponents/polyfills#260 · 2 comments · 0 reactions · 0 assignees · Indexed Sep 15, 2026
window.__shady_native_addEventListener is not a function in versions of Chrome and Firefox Open

Package: shadydom Type: Bug

webcomponents/polyfills#279 · 10 comments · 3 reactions · 0 assignees · Indexed Sep 15, 2026
[Template] If loaded after DOMContentLoaded, templates aren't upgraded Open

Package: template Type: Bug wontfix

webcomponents/polyfills#291 · 2 comments · 4 reactions · 1 assignee · Indexed Sep 15, 2026
Supporting ie11 and pass style attribute to the element Open

Focus Area: Standards & Polyfills Package: shadycss Type: Feature wontfix

webcomponents/polyfills#295 · 2 comments · 0 reactions · 0 assignees · Indexed Sep 15, 2026
Supporting ie11 and inheritance of css variable with slotted components Open

Focus Area: Standards & Polyfills Package: shadycss Type: Bug wontfix

webcomponents/polyfills#296 · 4 comments · 0 reactions · 0 assignees · Indexed Sep 15, 2026
Object doesn't support property or method '__shady_getRootNode' error thrown in Edge by version 2.2.10 and up. Open

Focus Area: Standards & Polyfills Package: shadydom Type: Bug wontfix

webcomponents/polyfills#298 · 2 comments · 0 reactions · 1 assignee · Indexed Sep 15, 2026
Publish shady-css-scoped-element Open

Focus Area: Standards & Polyfills Package: shady-css-scoped-element Type: Maintenance wontfix

webcomponents/polyfills#305 · 2 comments · 0 reactions · 0 assignees · Indexed Sep 15, 2026
Explainer for Shadow Parts support for native shadow DOM Open

Focus Area: Standards & Polyfills Type: Feature wontfix

webcomponents/polyfills#310 · 2 comments · 0 reactions · 1 assignee · Indexed Sep 15, 2026
Document shadycss limitation of custom properties and slotted children Open

Focus Area: Standards & Polyfills Package: shadycss Type: Maintenance wontfix

webcomponents/polyfills#316 · 2 comments · 0 reactions · 1 assignee · Indexed Sep 15, 2026
lit/polymer/polyfills uber test script Open

Focus Area: Standards & Polyfills Type: Maintenance wontfix

webcomponents/polyfills#317 · 2 comments · 0 reactions · 1 assignee · Indexed Sep 15, 2026

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