1. Rebeccapurple color

    The new color added in CSS Color Module Level 4

  2. #rrggbbaa hex color notation

    The CSS Color Module Level 4 defines new 4 & 8 character hex notation for color to include the opacity level.

  3. CSS Subgrid

    Feature of the CSS Grid Layout Module Level 2 that allows a grid-item with its own grid to align in one or both dimensions with its parent grid.

  4. 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.

  5. JavaScript modules via script tag

    Loading JavaScript module scripts (aka ES6 modules) using `<script type="module">` Includes support for the `nomodule` attribute.

  6. JavaScript modules: dynamic import()

    Loading JavaScript modules dynamically using the import() syntax

  7. CSS Flexible Box Layout Module

    Method of positioning elements in horizontal or vertical stacks. Support includes all properties prefixed with `flex`, as well as `display: flex`, `display: inline-flex`, `align-content`, `align-items`, `align-self`, `justify-content` and `order`.

  8. CSS Font Loading

    This CSS module defines a scripting interface to font faces in CSS, allowing font faces to be easily created and loaded from script. It also provides methods to track the loading status of an individual font, or of all the fonts on an entire page.

  9. HTML Imports

    Deprecated method of including and reusing HTML documents in other HTML documents. Superseded by ES modules.

  10. Resource Hints: modulepreload

    Using `<link rel="modulepreload">`, browsers can be informed to prefetch module scripts without having to execute them, allowing fine-grained control over when and how module resources are loaded.

  11. htmlscriptelement api: nomodule

  12. worker api: `worker()` constructor: support for ecmascript modules

  13. worklet api: addmodule

  14. css property: font-variant: css fonts module level 3 shorthand

  15. html element: link: rel: modulepreload

  16. html element: script: nomodule

  17. html element: script: type: module

  18. javascript built-in: webassembly: module

  19. javascript built-in: webassembly: module: customsections

  20. javascript built-in: webassembly: module: exports

  21. javascript built-in: webassembly: module: imports

  22. javascript built-in: webassembly: module: `module()` constructor

  23. javascript operator: await: use at module top level

  24. css 2.1 aural