1. Custom Elements (deprecated V0 spec)

    Original V0 version of the custom elements specification. See [Custom Elements V1](#feat=custom-elementsv1) for support for the latest version.

  2. Custom Elements (V1)

    One of the key features of the Web Components system, custom elements allow new HTML tags to be defined.

  3. dataset & data-* attributes

    Method of applying and accessing custom data to elements.

  4. window api: customelements

  5. html element: iframe: sandbox: `sandbox="allow-top-navigation-to-custom-protocols"`