1. :optional CSS pseudo-class

    The `:optional` pseudo-class matches form inputs (`<input>`, `<textarea>`, `<select>`) which are not `:required`.

  2. Form validation

    Method of setting required fields and field types without requiring JavaScript. This includes preventing forms from being submitted when appropriate, the `checkValidity()` method as well as support for the `:invalid`, `:valid`, and `:required` CSS pseudo-classes.

  3. beforeunloadevent api: user interaction required for dialog box

  4. cachestorage api: secure context required

  5. cryptokey api: secure context required

  6. crypto api: subtle: secure context required

  7. devicemotioneventacceleration api: secure context required

  8. devicemotioneventrotationrate api: secure context required

  9. elementinternals api: ariarequired

  10. element api: ariarequired

  11. gamepadbutton api: secure context required

  12. gamepadevent api: secure context required

  13. gamepadhapticactuator api: secure context required

  14. gamepadpose api: secure context required

  15. gamepad api: secure context required

  16. geolocationcoordinates api: secure context required

  17. geolocationpositionerror api: secure context required

  18. geolocationposition api: secure context required

  19. geolocation api: secure context required

  20. htmlinputelement api: required

  21. htmlselectelement api: required

  22. htmltextareaelement api: required

  23. mediadevices api: getusermedia: secure context required

  24. navigator api: activevrdisplays: secure context required

  25. navigator api: geolocation: secure context required

  26. navigator api: getgamepads: secure context required

  27. navigator api: mediadevices: secure context required

  28. navigator api: registerprotocolhandler: secure context required

  29. ndefmessage api: secure context required

  30. ndefreader api: secure context required

  31. ndefreadingevent api: secure context required

  32. ndefrecord api: secure context required

  33. notification api: secure context required

  34. positionoptions api: secure context required

  35. presentationrequest api: secure context required

  36. subtlecrypto api: secure context required

  37. svganimationelement api: requiredextensions

  38. svggraphicselement api: requiredextensions

  39. window api: ongamepadconnected: secure context required

  40. window api: ongamepaddisconnected: secure context required

  41. css selector: `:nth-child()`: matches elements with no parent

  42. css selector: `:required`

  43. html element: html: manifest: secure context required

  44. html element: link: prefetch: secure context required

  45. html element: select: required

  46. html element: textarea: required

  47. headers http header: clear-site-data: secure context required

  48. headers http header: set-cookie: `samesite`: secure context required

  49. javascript built-in: map: `map()` constructor: `map()` without `new` throws

  50. javascript built-in: set: `set()` constructor: `set()` without `new` throws