HTML5 video
Support for HTML5 video has been steadily increasing. In June 2013, Netflix added support for HTML5 video. In January 2015, YouTube switched to using HTML5 video instead of Flash by default. In December 2015, Facebook switched from Flash to HTML5 for all video content.
Internet Browser (Nintendo 3DS)
On the New 3DS, a new video player is integrated into the browser. It can play back both 2D and 3D Videos on webpages which supports HTML5. This eliminates the need for the dedicated YouTube app on the new 3DS.