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. document api: hidden

  6. elementinternals api: ariahidden

  7. element api: ariahidden

  8. htmlelement api: hidden

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

  10. html attribute: hidden

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