Comment by abraham

For a long time web components generally built on four standards:

  - Custom HTML elements
  - Shadow DOM
  - HTML imports
  - HTML templates

https://korban.net/posts/elm/2018-09-17-introduction-custom-...

Eventually it became clear some browsers were not going to implement and the design of HTML imports was better handled be ES modules.

https://webmasters.stackexchange.com/questions/127482/on-wha...