YouTube-videos sometimes not playing without Flash

I realize not all videos are playable without Flash just yet, but most do play perfectly without it these days, especially when embedded on other sites. However, playing those same videos directly on YouTube (or sometimes embedded on another site) doesn't work. It says Flash is required to view the video, which is clearly untrue since I just watched it.

Examples: Embedded YouTube-video plays here but not here for some odd reason.
Why would the same video (I checked the ID) play on the front page but not in the forums?
This particular video also works directly on YouTube, but my most common issue is with embedded videos not working there.
So it all seems a bit random to me and hard to figure out why it's happening.

First and foremost I am looking for an explanation to the phenomenon, but if a solution can also be found that would be welcomed as well.

Operating System: OS X 10.8.3 | Browser: Firefox 21.0 (stable) | Adobe Flash: Not installed

GGJstudios said:

The video plays for me in all locations. I use Flash on Safari with ClickToFlash to control which content plays, and I have zero issues with it.

For Flash-related issues:

• Find your Flash version and make sure it's the latest version available. Never install or update Flash from a pop-up on a website. Always go to Adobe's site to get Flash or updates.
• Install ClickToFlash (Safari), Flashblock (Firefox) or FlashBlock (Chrome) to control which Flash content plays on websites.
• Install ClickToPlugin (Safari) to prevent Safari from launching plug-ins automatically, resulting in faster browsing, reduced fan usage, and increased battery life. It can also replace many plug-in-based media players with Safari’s native HTML5 media player.
• Try using the YouTube HTML5 Video Player to watch YouTube videos, when available. (May impact fullscreen viewing. See link for details.) Some have reported better performance with HTML5, while some have reported worse. Try it and find out what works best for you.

Click to expand...

Way to miss the entire point of the thread.
Next time, spend another ten seconds reading the entire posts before posting an entirely irrelevant reply.

GGJstudios said:

I didn't miss the point and my reply is quite relevant. There is obviously something wrong on your end, since the videos play for me, embedded or not. I gave you things to check to diagnose the problem.

Click to expand...

It seems you still haven't actually read the post. I DO NOT HAVE FLASH INSTALLED.
This makes any information on how to find my version or update something I do not have, or installing plugins to block a plugin I do not even have installed quite pointless.

And the fact that it plays for you using Flash also seems quite irrelevant.
That's great for you and all, but this thread is about getting videos to play without Flash installed.

I appreciate the effort, but your entire post contributed absolutely nothing to this topic.

GGJstudios said:

I have, indeed, read and understood all of your post. It appears you haven't read all of mine, including the linked information. ClickToFlash and ClickToPlugin not only enable control over which Flash content is played, if you have Flash installed, they can also play Flash content with a HTML5 player.

Click to expand...

I know very well what ClickToFlash and the others do, but thanks for the explanation I guess.
But my point is that I obviously don't need any plugin(s) to block something I don't even have installed.
My question is why do videos that actually do play on some sites suddenly don't play on others.
Same video. Works on front page but not in forums. No Flash installed before or after. Isn't that odd?

Weaselboy said:

I see the exact same behavior you describe. Your first link to the video on the MacRumors front page works and the second link to the same video embedded in a forum post does not. I use Safari without Flash installed. If I open the second link in Chrome the video plays because Chrome uses its own, built in Flash.

The problem is the older version of VBulletin (V3) this forum uses does not seem to play embedded HTML5 Youtube videos. If you look at Youtube embedded video on forums that use the newer V4 of VBulletin, you will see they work fine in HTML5. For example, this forum post has a Youtube embed that works fine in HTML5.

Short answer is it is not you, it is the forum software used here.

Click to expand...

Thank you! Mystery solved at long last.
I kind of figured it wasn't on my end as it works in most places, but I was still curious as to why it happened.
Doesn't quite answer why it sometimes doesn't work directly on YouTube though.

Weaselboy said:

I think there are still some older Youtube videos that never got converted to the newer format for HTML5 playback. I can't remember the last time I ran across one though. Do you have a link to one on Youtube itself that won't play so I can test it on my machine?

Click to expand...

They're pretty rare, but I'm not so sure it has to do with age.
Here's one example of a recently uploaded video that doesn't play on YouTube.
Embedded (and working) here, directly on YouTube here.

Weaselboy said:

Those both work for me. I use this extension with the HTML5 beta turned off on YouTube and can't recall the last one that would not work directly on the Youtube. Maybe give the extension a shot. It won't help with the embedded forum videos though.

Click to expand...

That extension worked perfectly in Safari. I'm using Firefox however.
Is there a Firefox equivalent of this extension?