1. CSS3 selectors

    Advanced element selection using selectors including: `[foo^="bar"]`, `[foo$="bar"]`, `[foo*="bar"]`, `:root`, `:nth-child()`, `:nth-last-child()`, `:nth-of-type()`, `:nth-last-of-type()`, `:last-child`, `:first-of-type`, `:last-of-type`, `:only-child`, `:only-of-type`, `:empty`, `:target`, `:enabled`, `:disabled`, `:checked`, `:not()`, `~` (general sibling)

  2. DNSSEC and DANE

    Method of validating a DNS response against a trusted root server. Mitigates various attacks that could reroute a user to a fake site while showing the real URL for the original site.

  3. display: flow-root

    The element generates a block container box, and lays out its contents using flow layout. It always establishes a new block formatting context for its contents. It provides a better solution to the most use cases of the "clearfix" hack.

  4. rem (root em) units

    Type of unit similar to `em`, but relative only to the root element, not any parent element. Thus compounding does not occur as it does with `em` units.

  5. document api: rootelement

  6. elementinternals api: shadowroot

  7. element api: shadowroot

  8. filesystemsync api: root

  9. filesystem api: root

  10. htmltemplateelement api: shadowrootclonable

  11. htmltemplateelement api: shadowrootdelegatesfocus

  12. htmltemplateelement api: shadowrootmode

  13. htmltemplateelement api: shadowrootserializable

  14. intersectionobserverentry api: rootbounds

  15. intersectionobserver api: `intersectionobserver()` constructor: `options.root` parameter can be a `document`

  16. intersectionobserver api: root

  17. intersectionobserver api: rootmargin

  18. nodeiterator api: root

  19. node api: getrootnode

  20. shadowroot api

  21. shadowroot api: activeelement

  22. shadowroot api: adoptedstylesheets

  23. shadowroot api: clonable

  24. shadowroot api: delegatesfocus

  25. shadowroot api: elementfrompoint

  26. shadowroot api: elementsfrompoint

  27. shadowroot api: fullscreenelement

  28. shadowroot api: getanimations

  29. shadowroot api: gethtml

  30. shadowroot api: getselection

  31. shadowroot api: host

  32. shadowroot api: innerhtml

  33. shadowroot api: mode

  34. shadowroot api: pictureinpictureelement

  35. shadowroot api: pointerlockelement

  36. shadowroot api: serializable

  37. shadowroot api: sethtmlunsafe

  38. shadowroot api: slotassignment

  39. shadowroot api: stylesheets

  40. treewalker api: root

  41. css property: display: flow-root

  42. css selector: `:root`

  43. html element: template: shadowrootclonable

  44. html element: template: shadowrootmode