1. CSS3 Background-image options

    New properties to affect background images, including background-clip, background-origin and background-size

  2. Brotli Accept-Encoding/Content-Encoding

    More effective lossless compression algorithm than gzip and deflate.

  3. Web Cryptography

    JavaScript API for performing basic cryptographic operations in web applications

  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. :optional CSS pseudo-class

    The `:optional` pseudo-class matches form inputs (`<input>`, `<textarea>`, `<select>`) which are not `:required`.

  6. document.currentScript

    `document.currentScript` returns the `<script>` element whose script is currently being processed.

  7. Encrypted Media Extensions

    The EncryptedMediaExtenstions API provides interfaces for controlling the playback of content which is subject to a DRM scheme.

  8. ECMAScript 5

    Full support for the ECMAScript 5 specification. Features include `Function.prototype.bind`, Array methods like `indexOf`, `forEach`, `map` & `filter`, Object methods like `defineProperty`, `create` & `keys`, the `trim` method on Strings and many more.

  9. 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.

  10. JavaScript modules via script tag

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

  11. JavaScript modules: dynamic import()

    Loading JavaScript modules dynamically using the import() syntax

  12. crypto.getRandomValues()

    Method of generating cryptographically random values.

  13. HTML Media Capture

    Facilitates user access to a device's media capture mechanism, such as a camera, or microphone, from within a file upload control.

  14. ImageCapture API

    The Image Capture API provides access to the Video Camera for taking photos while configuring picture-specific settings such as e.g. zoom or auto focus metering area.

  15. accept attribute for file input

    Allows a filter to be defined for what type of files a user may pick with from an `<input type="file">` dialog

  16. Media Capture from DOM Elements API

    API to capture Real-Time video and audio from a DOM element, such as a `<video>`, `<audio>`, or `<canvas>` element via the `captureStream` method, in the form of a `MediaStream`

  17. Dynamic Adaptive Streaming over HTTP (MPEG-DASH)

    HTTP-based media streaming communications protocol, an alternative to HTTP Live Streaming (HLS).

  18. "once" event listener option

    Causes an event listener to be automatically removed after it gets invoked, so that it only gets invoked once. Similar to jQuery's `$.one()` feature.

  19. async attribute for external scripts

    The boolean async attribute on script elements allows the external JavaScript file to run when it's available, without delaying page load first.

  20. defer attribute for external scripts

    The boolean defer attribute on script elements allows the external JavaScript file to run when the DOM is loaded, without delaying page load first.

  21. SDCH Accept-Encoding/Content-Encoding

    Shared Dictionary Compression over HTTP

  22. ECMAScript 5 Strict Mode

    Method of placing code in a "strict" operating context.

  23. X-Frame-Options HTTP header

    An HTTP header which indicates whether the browser should allow the webpage to be displayed in a frame within another webpage. Used as a defense against clickjacking attacks.

  24. css api: pt

  25. rtcrtpencodingparameters api: ptime

  26. html element: caption

  27. html element: figcaption

  28. html element: noscript

  29. html element: optgroup

  30. html element: option

  31. html element: script

  32. javascript built-in: array: grouptomap

  33. javascript built-in: intl: collator: resolvedoptions

  34. javascript built-in: intl: datetimeformat: resolvedoptions

  35. javascript built-in: intl: displaynames: resolvedoptions

  36. javascript built-in: intl: listformat: resolvedoptions

  37. javascript built-in: intl: locale: script

  38. javascript built-in: intl: numberformat: resolvedoptions

  39. javascript built-in: intl: pluralrules: resolvedoptions

  40. javascript built-in: intl: relativetimeformat: resolvedoptions

  41. javascript built-in: intl: segmenter: resolvedoptions

  42. javascript built-in: nan

  43. javascript built-in: object: getownpropertydescriptor

  44. javascript built-in: object: getownpropertydescriptors

  45. javascript built-in: reflect: getownpropertydescriptor

  46. javascript built-in: set

  47. javascript built-in: symbol: description

  48. javascript function

  49. javascript operator: in

  50. javascript statement: empty statement (`;`)