1) Flash video clips, both recorded video and video animated with Flash shared on Newgrounds and the like.
The first group largely shifted to YouTube
YouTube, Dailymotion, Vimeo, and the like are fine for "recorded video" but inefficient for "video animated with Flash". Rendering a vector animation to pixels and then compressing the pixels bloats file size by a factor of 10 in my tests.
Adobe's replacement for Flash as a vector animation authoring tool is Animate CC, which can create vector animations for HTML5. The difference is that one can buy a used copy of an old version of Flash, but Animate is available only as a rental. So which other timeline-based* graphical applications, either free or purchased, can people use to create vector animations for HTML5?
* Typing coordinates into a text editor is not "timeline-based".