1. classList (DOMTokenList)

    Method of easily manipulating classes on elements, using the `DOMTokenList` object.

  2. Crisp edges/pixelated images

    Scales images with an algorithm that preserves edges and contrast, without smoothing colors or introducing blur. This is intended for images such as pixel art. Official values that accomplish this for the `image-rendering` property are `crisp-edges` and `pixelated`.

  3. :is() CSS pseudo-class

    The `:is()` (formerly `:matches()`, formerly `:any()`) pseudo-class checks whether the element at its position in the outer selector matches any of the selectors in its selector list. It's useful syntactic sugar that allows you to avoid writing out all the combinations manually as separate selectors. The effect is similar to nesting in Sass and most other CSS preprocessors.

  4. Datalist element

    Method of setting a list of options for a user to select in a text field, while leaving the ability to enter a custom value.

  5. 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`.

  6. HEIF/ISO Base Media File Format

    HEIF (High Efficiency Image File Format) is a standard developed by the Moving Picture Experts Group (MPEG) for storage and sharing of images and image sequences. Can use `.heif` or `.heic` file extensions.

  7. Page Visibility

    JavaScript API for determining whether a document is visible on the display

  8. Permissions API

    High-level JavaScript API for checking and requesting permissions

  9. 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).

  10. Promise.prototype.finally

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

  11. Promises

    A promise represents the eventual result of an asynchronous operation.

  12. credential api: isconditionalmediationavailable

  13. event api: istrusted

  14. external api: issearchproviderinstalled

  15. fetchevent api: isreload

  16. htmlelement api: iscontenteditable

  17. idbindex api: isautolocale

  18. inputevent api: iscomposing

  19. issecurecontext api

  20. issecurecontext api: available in workers

  21. mediasource api: istypesupported

  22. node api: isconnected

  23. node api: isdefaultnamespace

  24. node api: isequalnode

  25. node api: issamenode

  26. range api: ispointinrange

  27. scheduling api: isinputpending

  28. screen api: isextended

  29. selection api: iscollapsed

  30. usbdevice api: isochronoustransferin

  31. usbdevice api: isochronoustransferout

  32. xrview api: isfirstpersonobserver

  33. css property: isolation

  34. javascript built-in: arraybuffer: isview

  35. javascript built-in: array: isarray

  36. javascript built-in: atomics: islockfree

  37. javascript built-in: isfinite

  38. javascript built-in: isnan

  39. javascript built-in: number: isfinite

  40. javascript built-in: number: isinteger

  41. javascript built-in: number: isnan

  42. javascript built-in: number: issafeinteger

  43. javascript built-in: object: is

  44. javascript built-in: object: isextensible

  45. javascript built-in: object: isfrozen

  46. javascript built-in: object: isprototypeof

  47. javascript built-in: object: issealed

  48. javascript built-in: proxy: handler: isextensible

  49. javascript built-in: reflect: isextensible

  50. javascript built-in: symbol: isconcatspreadable