1. CSS overflow property

    Originally a single property for controlling overflowing content in both horizontal & vertical directions, the `overflow` property is now a shorthand for `overflow-x` & `overflow-y`. The latest version of the specification also introduces the `clip` value that blocks programmatic scrolling.

  2. hidden attribute

    The `hidden` attribute may be applied to any element, and effectively hides elements similar to `display: none` in CSS.

  3. Small, Large, and Dynamic viewport units

    Viewport units similar to `vw` and `vh` that are based on shown or hidden browser UI states to address shortcomings of the original units. Currently defined as the `sv*` units (`svb`, `svh`, `svi`, `svmax`, `svmin`, `svw`), `lv*` units (`lvb`, `lvh`, `lvi`, `lvmax`, `lvmin`, `lvw`), `dv*` units (`dvb`, `dvh`, `dvi`, `dvmax`, `dvmin`, `dvw`) and the logical `vi`/`vb` units.

  4. WAI-ARIA Accessibility features

    Method of providing ways for people with disabilities to use dynamic web content and web applications.

  5. console api: `dir()` static method: `options.showhidden` parameter

  6. document api: hidden

  7. elementinternals api: ariahidden

  8. element api: ariahidden

  9. htmlelement api: hidden

  10. css property: backface-visibility: hidden

  11. css property: border-block-end-style: hidden

  12. css property: border-block-end: hidden

  13. css property: border-block-start-style: hidden

  14. css property: border-block-start: hidden

  15. css property: border-block-style: hidden

  16. css property: border-block: hidden

  17. css property: border-bottom-style: hidden

  18. css property: border-bottom: hidden

  19. css property: border-inline-end-style: hidden

  20. css property: border-inline-end: hidden

  21. css property: border-inline-start-style: hidden

  22. css property: border-inline-start: hidden

  23. css property: border-inline-style: hidden

  24. css property: border-inline: hidden

  25. css property: border-left-style: hidden

  26. css property: border-left: hidden

  27. css property: border-right-style: hidden

  28. css property: border-right: hidden

  29. css property: border-style: hidden

  30. css property: border-top-style: hidden

  31. css property: border-top: hidden

  32. css property: border: hidden

  33. css property: column-rule-style: hidden

  34. css property: column-rule: hidden

  35. css property: content-visibility: hidden

  36. css property: display: none: setting `display: none` on an `<option>` element hides it from the dropdown.

  37. css property: overflow-block: hidden

  38. css property: overflow-inline: hidden

  39. css property: overflow-x: hidden

  40. css property: overflow-y: hidden

  41. css property: overflow: hidden

  42. css property: visibility: hidden

  43. html element: input: `type="hidden"`

  44. html attribute: hidden

  45. html attribute: hidden: `until-found` value