1. CSS3 Background-image options

    New properties to affect background images, including background-clip, background-origin and background-size

  2. :optional CSS pseudo-class

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

  3. "once" event listener option

    Causes an event listener to be automatically removed after it gets invoked, so that it only gets invoked once. Similar to jQuery's `$.one()` feature.

  4. X-Frame-Options HTTP header

    An HTTP header which indicates whether the browser should allow the webpage to be displayed in a frame within another webpage. Used as a defense against clickjacking attacks.

  5. cookiestore api: delete: `partitioned` option

  6. cookiestore api: set: `partitioned` option

  7. credentialscontainer api: create: `publickey` option

  8. credentialscontainer api: create: `publickey` option: `create()` extensions

  9. credentialscontainer api: create: `publickey` option: `create()` extensions: `appidexclude` extension

  10. credentialscontainer api: create: `publickey` option: `create()` extensions: `credprops` extension

  11. credentialscontainer api: create: `publickey` option: `create()` extensions: `credprotect` extension

  12. credentialscontainer api: create: `publickey` option: `create()` extensions: `largeblob` extension

  13. credentialscontainer api: create: `publickey` option: `create()` extensions: `minpinlength` extension

  14. credentialscontainer api: create: `publickey` option: `create()` extensions: `payment` extension

  15. credentialscontainer api: create: `publickey` option: requireresidentkey

  16. credentialscontainer api: create: `publickey` option: residentkey

  17. credentialscontainer api: get: `identity` option

  18. credentialscontainer api: get: `identity` option: `identity.context`

  19. credentialscontainer api: get: `identity` option: error api

  20. credentialscontainer api: get: `identity` option: `identity.providers.loginhint`

  21. credentialscontainer api: get: `otp` option

  22. credentialscontainer api: get: `publickey` option

  23. credentialscontainer api: get: `publickey` option: `get()` extensions

  24. credentialscontainer api: get: `publickey` option: `get()` extensions: `appid` extension

  25. credentialscontainer api: get: `publickey` option: `get()` extensions: `largeblob` extension

  26. cssstylesheet api: `insertrule()`: `index` parameter is optional

  27. gpupipelineerror api: `gpupipelineerror()` constructor: `message` parameter is optional

  28. htmldatalistelement api: options

  29. htmlselectelement api: options

  30. mediadevices api: `getdisplaymedia()`: `controller` option

  31. mediadevices api: `getdisplaymedia()`: `systemaudio` option

  32. pushsubscription api: options

  33. range api: collapse: `tostart` parameter is optional

  34. response api: `response()` constructor: `body` parameter is optional

  35. rtcrtpscripttransformer api: options

  36. selection api: collapse: `offset` parameter is optional

  37. selection api: extend: `offset` parameter is optional

  38. subtlecrypto api: derivekey: `aes` as `derivedkeyalgorithm` option value

  39. subtlecrypto api: derivekey: `hkdf` as `derivedkeyalgorithm` option value

  40. subtlecrypto api: derivekey: `hmac` as `derivedkeyalgorithm` option value

  41. urlpattern api: `urlpattern()` constructor: `ignorecase` option

  42. css property: border-image: optional `<border-image-slice>`

  43. html element: option

  44. html element: option: disabled

  45. html element: option: label

  46. html element: option: selected

  47. html element: option: value

  48. http method: options

  49. javascript operator: optional chaining operator (`?.`)

  50. javascript statement: `try...catch`: optional catch binding