1. Scoped Styles: the @scope rule

   Allows CSS rules to be scoped to part of the document, with upper and lower limits described by selectors.

2. ECMAScript 2015 (ES6)

   Support for the ECMAScript 2015 specification. Features include Promises, Modules, Classes, Template Literals, Arrow Functions, Let and Const, Default Parameters, Generators, Destructuring Assignment, Rest & Spread, Map/Set & WeakMap/WeakSet and many more.

3. Scoped attribute

   Deprecated method of allowing scoped CSS styles using a "scoped" attribute. Now [removed from the specification](https://github.com/whatwg/html/issues/552) and replaced by the [@scope CSS rule](/css-cascade-scope).