1. Beacon API

    Allows data to be sent asynchronously to a server with `navigator.sendBeacon`, even after a page was closed. Useful for posting analytics data the moment a user was finished using the page.

  2. CSS all property

    A shorthand property for resetting all CSS properties except for `direction` and `unicode-bidi`.

  3. CSS font-display

    `@font-face` descriptor `font-display` that allows control over how a downloadable font renders before it is fully loaded.

  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. CSS3 attr() function for all properties

    While `attr()` is supported for effectively all browsers for the `content` property, CSS Values and Units Level 3 adds the ability to use `attr()` on **any** CSS property, and to use it for non-string values (e.g. numbers, colors).

  6. Feature Policy

    This specification defines a mechanism that allows developers to selectively enable and disable use of various browser features and APIs. Feature Policy is deprecated and has been replaced with [Permissions Policy](/permissions-policy) and [Document Policy](/document-policy).

  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. Permissions Policy

    A security mechanism that allows developers to explicitly enable or disable various powerful browser features for a given site. Similar to [Document Policy](/document-policy).

  9. Promise.prototype.finally

    When the promise is settled, whether fulfilled or rejected, the specified callback function is executed.

  10. requestIdleCallback

    API allowing the execution of JavaScript to be queued to run in idle browser time, either at the end of a frame or when the user is inactive. Also covers support for `cancelIdleCallback`. The API has similarities with `requestAnimationFrame`.

  11. WebUSB

    Allows communication with devices via USB (Universal Serial Bus).

  12. CSS3 word-break

    Property to prevent or allow words to be broken over multiple lines between letters.

  13. document api: all

  14. featurepolicy api: allowedfeatures

  15. featurepolicy api: allowsfeature

  16. htmliframeelement api: allow

  17. htmliframeelement api: allowfullscreen

  18. htmliframeelement api: allowpaymentrequest

  19. publickeycredentialrequestoptions api: allowcredentials

  20. css property: all: `revert`

  21. css property: cursor: `all-scroll`

  22. css property: cursor: `not-allowed`

  23. css property: user-select: all

  24. css property: word-break: `keep-all`

  25. css selector: `:fullscreen`: select all elements in the fullscreen stack

  26. css selector: `:hover`: all elements support

  27. types: <color>: allow floats in `rgb()` and `rgba()`

  28. html element: iframe: allow

  29. html element: iframe: allowfullscreen

  30. html element: iframe: allowpaymentrequest

  31. html element: iframe: `sandbox="allow-downloads"`

  32. html element: iframe: `sandbox="allow-modals"`

  33. html element: iframe: `sandbox="allow-popups"`

  34. html element: iframe: `sandbox="allow-popups-to-escape-sandbox"`

  35. html element: iframe: `sandbox="allow-presentation"`

  36. html element: iframe: `sandbox="allow-same-origin"`

  37. html element: iframe: `sandbox="allow-storage-access-by-user-activation"`

  38. html element: iframe: `sandbox="allow-top-navigation-by-user-activation"`

  39. html element: small

  40. headers http header: access-control-allow-credentials

  41. headers http header: access-control-allow-headers

  42. headers http header: access-control-allow-headers: wildcard (`*`)

  43. headers http header: access-control-allow-methods

  44. headers http header: access-control-allow-methods: wildcard (`*`)

  45. headers http header: large-allocation

  46. headers http header: timing-allow-origin

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

  48. javascript built-in: promise: `all()`

  49. javascript built-in: promise: `allsettled()`

  50. svg element: switch: allowreorder