Disable all third-party Safari extensions and plugins, Input managers etc. and check if the problem disappears.
If it does, you can selectively enable and disable them to find the culprit.
Does it happen when you try youtube in incognito mode?
If so, try clearing the cache and cookies. If that doesn't fix it try disabling each extension you've installed, sometimes chrome extensions can cause problems with page rendering(eg:-adblock).
If that doesn't do it, turn off any flags you might have enabled in chrome://flags, or go to chrome's properties and insert "--no-experiments" without quotes in the target box to disable all flags:
![enter image description here](https://i.stack.imgur.com/8LrFR.png)
If it still doesn't work, you should try installing flash externally from this site
and then disabling the built in flash by going to "chrome://plugins", clicking on details in the right hand side of the screen, then navigating to Adobe Flash Player and disabling the plugin whose location is something like "Chrome\Application\26.0.1410.64\PepperFlash\pepflashplayer.dll
". Make sure that there is another entry under Adobe Flash Player that remains enabled.
![enter image description here](https://i.stack.imgur.com/WEMmG.png)
If the problem persists, try reinstalling chrome. If you have sync enabled, it shouldn't be too inconvenient.
Best Answer
You don't see the
video
tag if you just load the page source on its own. This is because thevideo
DOM element is added to the page dynamically, with JavaScript, and not even persisted in the page source.Here's the
video
tag in from your example:It's inserted through JavaScript inside
<div class="html5-remote-module">
after the video metadata and everything else has been loaded. One reason for not "hard-coding" thevideo
tag inside the page is that the link to the video resource has to be present inside the tag (as thesrc
attribute), and YouTube distributes the requests to a large number of caching servers rather than pointing to a single resource.