1. :placeholder-shown CSS pseudo-class

    Input elements can sometimes show placeholder text as a hint to the user on what to type in. See, for example, the placeholder attribute in HTML5. The :placeholder-shown pseudo-class matches an input element that is showing such placeholder text.

  2. Details & Summary elements

    The <details> element generates a simple no-JavaScript widget to show/hide element contents, optionally by clicking on its child <summary> element.

  3. Dialog element

    Method of easily creating custom dialog boxes to display to the user with modal or non-modal options. Also includes a `::backdrop` pseudo-element for behind the element.

  4. 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.

  5. Media Fragments

    Allows only part of a resource to be shown, based on the fragment identifier in the URL. Currently support is primarily limited to video track ranges.

  6. PageTransitionEvent

    Fired at the Window when the page's entry in the session history stops being the current entry. Includes the `pageshow` and `pagehide` events.

  7. 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.

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

  9. document api: createtreewalker: `whattoshow` and `filter` parameters are optional

  10. htmldialogelement api: show

  11. htmldialogelement api: showmodal

  12. htmlelement api: showpopover

  13. htmlinputelement api: showpicker

  14. htmlinputelement api: showpicker: `autocomplete` input

  15. htmlinputelement api: showpicker: `color` input

  16. htmlinputelement api: showpicker: `datalist` input

  17. htmlinputelement api: showpicker: `datetime-local` input

  18. htmlinputelement api: showpicker: `date` input

  19. htmlinputelement api: showpicker: `file` input

  20. htmlinputelement api: showpicker: `month` input

  21. htmlinputelement api: showpicker: `time` input

  22. htmlinputelement api: showpicker: `week` input

  23. htmlselectelement api: showpicker

  24. nodeiterator api: whattoshow

  25. notification api: `show` event

  26. paymentrequest api: show

  27. serviceworkerregistration api: shownotification

  28. serviceworkerregistration api: shownotification: `options.actions` parameter

  29. serviceworkerregistration api: shownotification: `options.badge` parameter

  30. serviceworkerregistration api: shownotification: `options.data` parameter

  31. serviceworkerregistration api: shownotification: `options.image` parameter

  32. serviceworkerregistration api: shownotification: `options.renotify` parameter

  33. serviceworkerregistration api: shownotification: `options.requireinteraction` parameter

  34. serviceworkerregistration api: shownotification: `options.vibrate` parameter

  35. treewalker api: whattoshow

  36. virtualkeyboard api: show

  37. window api: `pageshow` event

  38. window api: showdirectorypicker

  39. window api: showmodaldialog

  40. window api: showopenfilepicker

  41. window api: showsavefilepicker

  42. css selector: `:placeholder-shown`: support on non-`type="text"` elements (such as `type="number"` or `type="time"`)

  43. svg element: a: `xlink:show`