1. Array.prototype.includes

    Determines whether or not an array includes the given value, returning a boolean value (unlike `indexOf`).

  2. Audio element

    Method of playing sound on webpages (without requiring a plug-in). Includes support for the following media properties: `currentSrc`, `currentTime`, `paused`, `playbackRate`, `buffered`, `duration`, `played`, `seekable`, `ended`, `autoplay`, `loop`, `controls`, `volume` & `muted`

  3. Constraint Validation API

    API for better control over form field validation. Includes support for `checkValidity()`, `setCustomValidity()`, `reportValidity()` and validation states.

  4. CSS Device Adaptation

    Method of overriding the size of viewport in web page using the `@viewport` rule, replacing Apple's own popular `<meta>` viewport implementation. Includes the `extend-to-zoom` width value.

  5. CSS Grid Layout (level 1)

    Method of using a grid concept to lay out content, providing a mechanism for authors to divide available space for layout into columns and rows using a set of predictable sizing behaviors. Includes support for all `grid-*` properties and the `fr` unit.

  6. Media Queries: interaction media features

    Allows a media query to be set based on the presence and accuracy of the user's pointing device, and whether they have the ability to hover over elements on the page. This includes the `pointer`, `any-pointer`, `hover`, and `any-hover` media features.

  7. CSS3 Media Queries

    Method of applying styles based on media information. Includes things like page and device dimensions

  8. CSS Shapes Level 1

    Allows geometric shapes to be set in CSS to define an area for text to flow around. Includes properties `shape-outside`, `shape-margin` and `shape-image-threshold`

  9. CSS Table display

    Method of displaying elements as tables, rows, and cells. Includes support for all `display: table-*` properties as well as `display: inline-table`

  10. Dialog element

    Method of easily creating custom dialog boxes to display to the user with modal or non-modal options. Also includes a `::backdrop` pseudo-element for behind the element.

  11. DOM manipulation convenience methods

    jQuery-like methods on DOM nodes to insert nodes around or within a node, or to replace one node with another. These methods accept any number of DOM nodes or HTML strings as arguments. Includes: `ChildNode.before`, `ChildNode.after`, `ChildNode.replaceWith`, `ParentNode.prepend`, and `ParentNode.append`.

  12. 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.

  13. JavaScript modules via script tag

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

  14. String.prototype.includes

    The includes() method determines whether one string may be found within another string, returning true or false as appropriate.

  15. 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`.

  16. Form validation

    Method of setting required fields and field types without requiring JavaScript. This includes preventing forms from being submitted when appropriate, the `checkValidity()` method as well as support for the `:invalid`, `:valid`, and `:required` CSS pseudo-classes.

  17. PageTransitionEvent

    Fired at the Window when the page's entry in the session history stops being the current entry. Includes the `pageshow` and `pagehide` events.

  18. CSS3 2D Transforms

    Method of transforming an element including rotating, scaling, etc. Includes support for `transform` as well as `transform-origin` properties.

  19. CSS3 3D Transforms

    Method of transforming an element in the third dimension using the `transform` property. Includes support for the `perspective` property to set the perspective in z-space and the `backface-visibility` property to toggle display of the reverse side of a 3D-transformed element.

  20. Typed Arrays

    JavaScript typed arrays provide a mechanism for accessing raw binary data much more efficiently. Includes: `Int8Array`, `Uint8Array`, `Uint8ClampedArray`, `Int16Array`, `Uint16Array`, `Int32Array`, `Uint32Array`, `Float32Array` & `Float64Array`

  21. Video element

    Method of playing videos on webpages (without requiring a plug-in). Includes support for the following media properties: `currentSrc`, `currentTime`, `paused`, `playbackRate`, `buffered`, `duration`, `played`, `seekable`, `ended`, `autoplay`, `loop`, `controls`, `volume` & `muted`

  22. idbkeyrange api: includes

  23. css property: text-decoration: `text-decoration-color` and `text-decoration-style` included in shorthand

  24. css property: text-decoration: `text-decoration-thickness` included in shorthand

  25. javascript built-in: typedarray: includes

  26. ecmascript 2016 (es7)