Mac OS Sierra Safari Youtube Flash out-of-date I am using Mac OS Sierra 10.12.5 (16F73) and Safari 10.1.1 (12603.2.4).

When I visit youtube most videos play fine. but some videos say

Flash out-of-date


It also quickly bring up a prompt to say "upgrade flash" which leads me to Adobe website.

But wasn't flash totally discontinued on Mac and Safari? if so, why am I being asked to upgrade flash?

I don't want Flash on my machine. 

My understanding was that Youtube/Safari should use everything as HTML5 (H264) stuff. Then what's going on?
Flash is still [barely] alive &amp; kicking, though is not needed at all for YouTube these days.

The best way to ensure it's gone once &amp; for all is to use the dedicated uninstaller, available from Adobe, at Adobe KB: Uninstall Flash Player | Mac OS

The uninstaller is Mac version-dependant, but the direct link for OS X 10.6 &amp; later is at https://fpdownload.macromedia.com/get/flashplayer/current/support/uninstall_flash_player_osx.dmg