In general, it was awkward to rely on plugins for video support, so flash was indeed generally used. Here's a 2015 article referencing YouTube dropping flash f

In general, it was awkward to rely on plugins for video support, so flash was indeed generally used. Here's a 2015 article referencing YouTube dropping flash for it's HTML5 player: https://www.theverge.com/2015/1/27/7926001/youtube-drops-flash-for-html5-video-default https://www.theverge.com/2015/1/27/7926001/youtube-drops-fla... The article touches on the challenge of getting to that point.