1. Audio Tracks

    Method of specifying and selecting between multiple audio tracks. Useful for providing audio descriptions, director's commentary, additional languages, alternative takes, etc.

  2. CSS font-stretch

    If a font has multiple types of variations based on the width of characters, the `font-stretch` property allows the appropriate one to be selected. The property in itself does not cause the browser to stretch to a font.

  3. selector list argument of :not()

    Selectors Level 3 only allowed `:not()` pseudo-class to accept a single simple selector, which the element must not match any of. Thus, `:not(a, .b, [c])` or `:not(a.b[c])` did not work. Selectors Level 4 allows `:not()` to accept a list of selectors. Thus, `:not(a):not(.b):not([c])` can instead be written as `:not(a, .b, [c])` and `:not(a.b[c])` works as intended.

  4. CSS Regions

    Method of flowing content into multiple elements, allowing magazine-like layouts. While once supported in WebKit-based browsers and Internet Explorer, implementing the feature is no longer being pursued by any browser.

  5. CSS text-wrap: balance

    Allows multiple lines of text to have their lines broken in such a way that each line is roughly the same width, often used to make headlines more readable and visually appealing.

  6. Multiple file selection

    Allows users to select multiple files in the file picker.

  7. CSS3 Multiple backgrounds

    Method of using multiple images as a background

  8. CSS3 Multiple column layout

    Method of flowing information in multiple columns

  9. Shared Web Workers

    Method of allowing multiple scripts to communicate with a single web worker.

  10. Variable fonts

    OpenType font settings that allows a single font file to behave like multiple fonts: it can contain all the allowed variations in width, weight, slant, optical size, or any other exposed axes of variation as defined by the font designer. Variations can be applied via the `font-variation-settings` property.

  11. Video Tracks

    Method of specifying and selecting between multiple video tracks. Useful for providing sign language tracks, burnt-in captions or subtitles, alternative camera angles, etc.

  12. WebAssembly Multi-Value

    An extension to WebAssembly allowing instructions, blocks and functions to produce multiple result values

  13. WebAssembly Reference Types

    An extension to WebAssembly allowing opaque references as first-class types, and multiple tables

  14. WebTransport

    Protocol framework to send and receive data from servers using [HTTP3](/http3). Similar to [WebSockets](/websockets) but with support for multiple streams, unidirectional streams, out-of-order delivery, and reliable as well as unreliable transport.

  15. CSS3 word-break

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

  16. domtokenlist api: add: multiple parameters for `add()`

  17. domtokenlist api: remove: multiple parameters for `remove()`

  18. htmlinputelement api: multiple

  19. htmlselectelement api: multiple

  20. css property: background-attachment: multiple backgrounds

  21. css property: background-image: multiple backgrounds

  22. css property: background-position: multiple backgrounds

  23. css property: background-repeat: multiple backgrounds

  24. css property: background: multiple backgrounds

  25. css property: box-shadow: multiple shadows

  26. css property: mask-image: multiple mask images

  27. css property: overflow: multiple keyword syntax for `overflow-x` and `overflow-y`

  28. html element: input: multiple

  29. html element: select: multiple