1. Audio Tracks

    Method of specifying and selecting between multiple audio tracks. Useful for providing audio descriptions, director's commentary, additional languages, alternative takes, etc.

  2. CSS text-box-trim & text-box-edge

    Provides the ability to remove the vertical space appearing above and below text glyphs, allowing more precise positioning and alignment. Previously specified as the `leading-trim` & `text-edge` properties.

  3. CSS3 Transitions

    Simple method of animating certain properties of an element, with ability to define property, duration, delay and timing function.

  4. Do Not Track API

    API to allow the browser's Do Not Track setting to be queried via `navigator.doNotTrack`. Due to lack of adoption the Do Not Track specification was deprecated in 2018.

  5. 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.

  6. PNG alpha transparency

    Semi-transparent areas in PNG files

  7. CSS3 2D Transforms

    Method of transforming an element including rotating, scaling, etc. Includes support for `transform` as well as `transform-origin` properties.

  8. CSS3 3D Transforms

    Method of transforming an element in the third dimension using the `transform` property. Includes support for the `perspective` property to set the perspective in z-space and the `backface-visibility` property to toggle display of the reverse side of a 3D-transformed element.

  9. Trusted Types for DOM manipulation

    An API that forces developers to be very explicit about their use of powerful DOM-injection APIs. Can greatly improve security against XSS attacks.

  10. TTF/OTF - TrueType and OpenType font support

    Support for the TrueType (.ttf) and OpenType (.otf) outline font formats in @font-face.

  11. Video Tracks

    Method of specifying and selecting between multiple video tracks. Useful for providing sign language tracks, burnt-in captions or subtitles, alternative camera angles, etc.

  12. WebVTT - Web Video Text Tracks

    Format for marking up text captions for multimedia resources.

  13. trackevent api

  14. trackevent api: track

  15. transitionevent api

  16. transitionevent api: elapsedtime

  17. transitionevent api: propertyname

  18. transitionevent api: pseudoelement

  19. treewalker api

  20. treewalker api: currentnode

  21. treewalker api: filter

  22. treewalker api: firstchild

  23. treewalker api: lastchild

  24. treewalker api: nextnode

  25. treewalker api: nextsibling

  26. treewalker api: parentnode

  27. treewalker api: previousnode

  28. treewalker api: previoussibling

  29. treewalker api: root

  30. treewalker api: whattoshow

  31. trustedhtml api

  32. trustedhtml api: tojson

  33. trustedscript api

  34. trustedscripturl api

  35. trustedscripturl api: tojson

  36. trustedscript api: tojson

  37. trustedtypepolicy api

  38. trustedtypepolicyfactory api

  39. trustedtypepolicyfactory api: ishtml

  40. trustedtypepolicyfactory api: isscript

  41. trustedtypepolicy api: createhtml

  42. trustedtypepolicy api: createscript

  43. trustedtypepolicy api: createscripturl

  44. trustedtypepolicy api: name

  45. trustedtypes api

  46. trustedtypes api: available in workers

  47. html element: tr

  48. html element: track

  49. javascript built-in: math: trunc

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