[cpeterso]

One advantage of Flash over HTML5 video (in Firefox, at least) is that Flash has its own H.264 decoder for platforms that don't include one (like Windows XP or the "N/KN editions" of Windows for Europe and Korea). Flash can also use the GPU for decoding or compositing of video on XP, providing better performance than Firefox playing VP9 using a software decoder.

YouTube recently relegated Flash to the bottom of its list of preferred video formats. Firefox users on XP who used to get hardware-accelerated 1080p video using Flash now get VP9. Many older XP machines can't keep up decoding VP9 in software. I recommend Firefox users on XP install the "YouTube Flash Video Player" add-on, which will force YouTube to use Flash again:

https://addons.mozilla.org/en-US/firefox/addon/youtube-flash...

[cooper12]

Youtube also serves VP9 in preference to H.264 in general. I had to install a browser extension to trick it that my browser doesn't support it so I'd get hardware acceleration. I don't know if the decision is based on ideology or bandwidth savings, but it certainly isn't nice on my CPU.

[Pxtl]

XP machines? In 2016? That's solving the wrong problem.

[cpeterso]

XP is still a big problem. About 14% of Firefox users are running XP, about the same share as running Windows 10. Google says they will drop support for Chrome on XP and Vista in April 2016. They already extended their XP EOL twice before (from December 2015 and April 2015), so there's a good chance they will need to do it again.

[Pxtl]

I had an old Xp-based laptop running as a file-and-print server. It was behind a router, so not even fully public. Nothing was even running on it besides SMB shares, VNC, and a media server.

Some kind of botnet must have hit it, because one day I got a bandwidth-consumption notice from my ISP and found that an SSH server and a torrent system had been installed.