The 9KB download requires Safari 5 and works like a charm under OS X Lion, especially used with Click2Flash, a Flash-blocking plug-in for Safari. The FlashtoHTML5 extension is available here. One caveat: The extension depends upon whether or not YouTube has HTML5-friendly counterparts of Flash videos available on its servers.
Of course, YouTube has had an experimental HTML5 video player available for some time now, but Vervuurt’s dedicated extension beats YouTube’s solution on ease of use and the ability to choose maximum video resolution (360p, 720p, 1080p and 4K), plus it works with Flash videos embedded on other sites.
The extensions has a sole purpose: It replaces the CPU-hogging YouTube Flash Player with an HTML5 video player. That said, the FlashtoHTML5 extension from Joris Vervuurt was Godsent. I’ve vowed never to install anything from Adobe again on my brand spanking new MacBook Air as I only allow Adobe software on my Mac mini, which I relegated to my testing machine and media center. This leaves us with three choices: Avoid Flash content altogether (possible, but hardly an option for mainstream folks), switch to Google’s Chrome browser that comes with the latest version of Flash Player built-in (a forced option for Safari fans) or just install the darn thing and deal with consequences later. And lastly, even for genuine flash content that you care about, it would still. Not to mention it would also cause a lot more data to be downloaded for each web page as Safari has to download all of the flash advertising. It would probably cut the battery time of the iPhone down to about 2 hours. As you know, OS X Lion ships without Flash Player to the delight of fans in support of Apple’s ongoing argument against Adobe’s resource-hungry technology. Flash is horribly slow and a huge resource hog.