HTML Imports are deprecated at M70, and will be removed in M80, by February, 2020. Please see this post for more information: https://developers.google.com/web/updates/2019/07/web-components-time-to-upgrade For the original Intent to Deprecate: https://groups.google.com/a/chromium.org/d/msg/blink-dev/h-JwMiPUnuU/sl79aLoLBQAJ HTML Imports was an experimental technology, never implemented in any other browser. The spec is superseded by ES modules, which is widely supported.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.
Docs: https://developers.google.com/web/updates/2019/07/web-components-time-to-upgrade http://www.html5rocks.com/tutorials/webcomponents/imports/ https://developer.mozilla.org/en-US/docs/Web/Web_Components/HTML_Imports