Custom Elements v0 is deprecated at M70, and will be removed in M80, by February, 2020. Please see this post for more information: For the original Intent to Deprecate: Custom Elements v0 was an experimental technology, never implemented in any other browser. The spec is superseded by Custom Elements v1, which is widely supported.


Shadow DOM V0, Custom Elements V0, and HTML Imports were launched in 2014, but they did not get adopted by other browser engines. Instead, Shadow DOM V1, Custom Elements V1, and ES modules are widely adopted by various browser engines today. Chrome has shipped Shadow DOM V1 / Custom Elements V1 in 2016 and ES modules in 2017.



Specification link

Unknown standards status - check spec link for status

Status in Chromium


Removed (tracking bug)

Consensus & Standardization

After a feature ships in Chrome, the values listed here are not guaranteed to be up to date.

  • No signal
  • No signal
  • Positive



Edge's signal should be treated for implementing V1 spec. Firefox once implemented behind the flag, but removed in favor of V1 APIs. Safari did not implement Custom Elements V0 spec, but already implemented V1 APIs and shipped it.

Last updated on 2022-01-14