1. Scoped Styles: the @scope rule

    Allows CSS rules to be scoped to part of the document, with upper and lower limits described by selectors.

  2. CSS clip-path property (for HTML)

    Method of defining the visible region of an HTML element using SVG or a shape definition.

  3. CSS Filter Effects

    Method of applying filter effects using the `filter` property to elements, matching filters available in SVG. Filter functions include blur, brightness, contrast, drop-shadow, grayscale, hue-rotate, invert, opacity, sepia and saturate.

  4. :focus-within CSS pseudo-class

    The `:focus-within` pseudo-class matches elements that either themselves match `:focus` or that have descendants which match `:focus`.

  5. selector list argument of :nth-child and :nth-last-child CSS pseudo-classes

    The newest versions of `:nth-child()` and `:nth-last-child()` accept an optional `of S` clause which filters the children to only those which match the selector list `S`. For example, `:nth-child(1 of .foo)` selects the first child among the children that have the `foo` class (ignoring any non-`foo` children which precede that child). Similar to `:nth-of-type`, but for arbitrary selectors instead of only type selectors.

  6. disabled attribute of the fieldset element

    Allows disabling all of the form control descendants of a fieldset via a `disabled` attribute on the fieldset element itself.

  7. CSS font-smooth

    Controls the application of anti-aliasing when fonts are rendered.

  8. Input Method Editor API

    Provides scripted access to the Input Method Editor (IME). An IME is often used to input characters from East Asian languages by typing roman characters and selecting from the resulting suggestions.

  9. maxlength attribute for input and textarea elements

    Declares an upper bound on the number of characters the user can input. Normally the UI ignores attempts by the user to type in additional characters beyond this limit.

  10. theme-color Meta Tag

    Meta tag to define a suggested color that browsers should use to customize the display of the page or of the surrounding user interface. The meta tag overrides any theme-color set in the web app manifest.

  11. Ogg/Theora video format

    Free lossy video compression format.

  12. Path2D

    Allows path objects to be declared on 2D canvas surfaces

  13. WebAssembly Threads and Atomics

    An extension to WebAssembly adding shared memory and atomic memory operations

  14. Web Bluetooth

    Allows web sites to communicate over GATT with nearby user-selected Bluetooth devices in a secure and privacy-preserving way.

  15. Web Authentication API

    The Web Authentication API is an extension of the Credential Management API that enables strong authentication with public key cryptography, enabling password-less authentication and / or secure second-factor authentication without SMS texts.

  16. abortsignal api: throwifaborted

  17. htmltableelement api: thead

  18. css property: border: thick

  19. css property: border: thin

  20. css property: outline: thick

  21. css property: outline: thin

  22. html element: th

  23. html element: thead

  24. html element: thead: align

  25. html element: thead: bgcolor

  26. html element: thead: char

  27. html element: thead: charoff

  28. html element: thead: valign

  29. html element: th: abbr

  30. html element: th: align

  31. html element: th: axis

  32. html element: th: bgcolor

  33. html element: th: char

  34. html element: th: charoff

  35. html element: th: colspan

  36. html element: th: headers

  37. html element: th: rowspan

  38. html element: th: scope

  39. html element: th: valign

  40. javascript built-in: asyncgenerator: throw

  41. javascript built-in: generator: throw

  42. javascript built-in: promise: `then()`

  43. javascript operator: this

  44. javascript statement: throw

  45. webapp: theme_color

  46. attribute_values: nonzero unitless values (e.g. 5 to mean 500% the default thickness)

  47. threads-and-atomics