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Web Components

Web Components is a set of specs which let web developers leverage their HTML, CSS and JavaScript knowledge to build widgets that can be reused easily and reliably.

This page is about the implementation of Web Components in Blink. If this was not what you are looking for, maybe one of these links will help:

 I want to...  You should try...
 Get a high-level overview of the Web Components specs  Introduction to Web Components
 Contribute to the development of Web Components specs  The Web Applications (WebApps) Working Group
 Learn how to use Web Components in a page  Posts on HTML5Rocks tagged WebComponents
 Ask a question about using Web Components in a page  Stack Overflow (web-component tagshadow-dom tag)
 Find people talking about Web Components  Web Components on Google+; "web components" on Twitter
 Find out more about Custom Elements  Custom Elements on HTML5Rocks. A YouTube video.


  Canary (Chrome 34)  Dev (Chrome 33)  Beta (Chrome 32)  Stable (Chrome 31)
Custom Elements c b a a
Shadow DOM
HTML Imports

✕ - Not Available
△ - Available behind a flag
❍ - Available

a Notes:
  • Requires the Experimental WebKit Features/Enable experimental Web Platform features flag.
b Notes:
  • document.register is now document.registerElement
  • enteredVIewCallback and leftViewCallback are now attachedCallback and detachedCallback
  • The deprecated document.webkitRegister method has been removed completely.
  • Elements are upgraded in document order. They used to be upgraded in the order their end tags were encountered (post order).
  • When the template document is a separate document, it does not share Custom Element definitions with the main document. This means Custom Elements in templates are inert by default.
  • As always, less crashy :)
c Notes:
  • When paused in the debugger Custom Element callbacks continue to run. Previously a bug caused them to be silently dropped.

Issue Tracking

Web Components bugs are tracked in the Chromium Issue Tracker using these tags:

 Tag  Purpose 
 Cr-Blink-WebComponents  All issues related to Web Components
 Hotlist-Toolkit  Issues blocking toolkits using Web Components
 Type-Bug (and related sub-tags)  Defects
 Type-Feature  New features 

Links we use to triage and tackle issues.

 Link  Purpose 
Untriaged / Unconfirmed  Triage
WebComponents × Hotlist-Toolkit  To tackle issues blocking toolkits using Web Components
Hotlist-Toolkit bugs closed last week  To review