joakimwallden - yes, I tried to add exception and it did not help. I use Opera 24.0.1558.53 on Mac with Flash PLayer 14.0.0.176

rafaelluik - what about this patch? How can I uninstall it?

I don't know why I can't add youtube link to video
https://www.youtube.com/watch?v=VxvDVhjALoU

Unfortunately not. I don't know if you properly understand what is my issue.

1. When I set: player html5 and flash plugin enabled, EVERY youtube video is opened as flash.
2. When I set: player html5 and flush plugin disabled, most youtube videos are opened as html5 objects.

Am I the one person how have this issue?

Please try to play e.g.:
https://www.youtube.com/watch?v=VxvDVhjALoU

with setting 1) - do you see flash or html5 video?

Unfortunately not. I don't know if you properly understand what is my issue.

1. When I set: player html5 and flash plugin enabled, EVERY youtube video is opened as flash.
2. When I set: player html5 and flush plugin disabled, most youtube videos are opened as html5 objects.

Am I the one person how have this issue?

Please try to play e.g. https://www.youtube.com/watch?v=VxvDVhjALoU with setting 1) - do you see flash or html5 video?

Thanks for reply. I HAVE html5-player enabled. But most videos are probably coded in vp8, because after opening video, for a second is shown message that codec is missing and player is automaticaly switched to flash version. If these videos would be in vp9, they were opened by html5 player.
When I turn off flash plugin, then the same video is properly played as html5.

I found an issue with WebM VP8 codec - when Flash plugin is enabled, Opera stops using WebM VP8. This causes problems when using Youtube. I'd like to play yt movies on html5, but most of them are coded by webm vp8. Flash plugin disables possibility of play as html5 and forces to play as flash video.

Is there any way to have installed and enabled Flash plugin and at the same time play youtube videos as html5 webm vp8?

Here is when flash plugins disabled:
http://i.imgur.com/Pev3eTB.png

Here - when flash is enabled:
http://i.imgur.com/MJU5hEn.png