1. BroadcastChannel

    BroadcastChannel allows scripts from the same origin but other browsing contexts (windows, workers) to send each other messages.

  2. CSS background-position edge offsets

    Allows CSS background images to be positioned relative to the specified edge using the 3 to 4 value syntax. For example: `background-position: right 5px bottom 5px;` for positioning 5px from the bottom-right corner.

  3. CSS font-palette

    The font-palette CSS property allows selecting a palette from a color font. In combination with the `@font-palette-values` at-rule, custom palettes can be defined.

  4. CSS hanging-punctuation

    Allows some punctuation characters from start (or the end) of text elements to be placed "outside" of the box in order to preserve the reading flow.

  5. CSS Relative colors

    The CSS Relative Color syntax allows a color to be defined relative to another color using the `from` keyword and optionally `calc()` for any of the color values.

  6. EOT - Embedded OpenType fonts

    Type of font that can be derived from a regular font, allowing small files and legal use of high-quality fonts. Usage is restricted by the file being tied to the website

  7. 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.

  8. 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

  9. Directory selection from file input

    The `webkitdirectory` attribute on the `<input type="file">` element allows entire directory with file contents (and any subdirectories) to be selected.

  10. Media Source Extensions

    API allowing media data to be accessed from HTML `video` and `audio` elements.

  11. Push API

    API to allow messages to be pushed from a server to a browser, even when the site isn't focused or even open in the browser.

  12. 'SameSite' cookie attribute

    Same-site cookies ("First-Party-Only" or "First-Party") allow servers to mitigate the risk of CSRF and information leakage attacks by asserting that a particular cookie should only be sent with requests initiated from the same registrable domain.

  13. 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).

  14. Signed HTTP Exchanges (SXG)

    Part of the Web Packaging spec, Signed HTTP Exchanges allow a different origin server to provide a resource, and this will be treated as if it came from the original server. This can be used with AMP CDNs, for example, to allow the original URL to be displayed in the URL bar.

  15. mediasession api

  16. headers http header: x-frame-options: allow-from