YouTube video quality using Safari 9.0 on OS X 10.9.5

I have the same issue, no fix yet. Chrome works OK.

Exactly the same thing happened to me. I am still using Mavericks 10.9.5 and don't want to upgrade because of compatibility issues with apps I'm using. I've been trying everything. Even spent three hours on the phone with the first tier and then a senior AppleCare adviser, to no avail. Not wanting to send logs of my Computer to Apple ,which the senior advisor almost rushed me into doing, he then said he was 99 % sure they would tell me to upgrade to El Capitan. I think this is very disingenuous of Apple to release Safari 9 saying it is for Mavericks also when it's not fully functional in Mavericks. I tried it in a test user account and it had the same problem; the senior advisor also created a disk partition and installed OS X, which came with Safari 7.0.6, which didn't work for 1080p ,which was upgraded then to Safari 9, which didn't get 1080p either. The only thing that seemed to get it, with the first advisor, was in safe mode--although everything loaded slowly and the video screen was black and would not play, when the resolutions came through, 1080p was available. I don't know why it would do that in safe mode and nowhere else. The senior adviser did say maybe an update would fix it; we will see.

By the way, Firefox works fine getting 1080p on YouTube with HTML5,

I do not have any Firefox Flash add-ons. Does Firefox include flash natively? Because I had uninstalled Flash player before reinstalling it, and while it was uninstalled I viewed YouTube videos in Firefox in the higher 1080p resolution, so I was assuming that HTML5 was working in that resolution in Firefox. So I'm not sure if it's a flash problem or a problem with the HTML5 version as used by Safari 9 in Mavericks. Does Safari 9 work to display 1080p on YouTube without using Flash in El Capitan, or does it use Flash there? The first AppleCare advisor also tested an Apple generated 1080p trailer as played through my Safari 9 browser, and it only showed 720p at the highest, so it is not exclusively a YouTube problem, as flash player seems to be deactivated in Safari 9, at least with Mavericks 10.9.5. I really hope they fix this soon.

Whatever the issue, and the AppleCare senior adviser even suggested using a different browser until it is resolved, rather than your method which requires resetting every time, apparently, I made Firefox my default browser, and spent a couple hours formatting it, reproducing the toolbar buttons for favorite sites, adding the Self-Destructing Cookies add-on to clear cookies automatically, but more importantly to save the ones from Google and YouTube, as they are required to retain sign in information as of a number of months ago, it seems, and signing into various sites I visit to save the password info in Firefox. I also added Adblock Plus to reproduce the effect of AdBlock in Safari. It's too bad, because Safari 9 added some nice text font changes. At least I have Firefox set up in case I want to use it also if Safari ever becomes functional again.

Strangely I have some videos that have the ability to play at 480p, I can't play at higher quality because of my internet speed, but other videos don't have that option.

I mentioned on a couple other threads that Apple has verified, after a senior advisor working with me sent them logs of the problem, that Safari 9, only and Mavericks, is not employing Media Source Extensions, which is what it needs for 1080p video on YouTube and even within Apple, as they do not use flash anymore. I was told that this would be corrected in an update, but it's been a month since they realized the problem and no fix has been issued. Are others still having the problem in Mavericks?

Yea, they still haven't fixed it.

Approaching the end of February, 2016, and no fix from Apple yet.
I won't upgrade from Mavericks. Not an option after actually having to downgrade from Yosemite & El Capitan since it was way too slow for my Mid-2010 17" on Core i7, 8GB of RAM and two SSDs...

I was told a couple months ago by a senior AppleCare advisor who passed my questions on to the engineering department, that Apple will not be fixing the issue. Apparently, unlike other browsers that include the missing component that is causing the problem, Media Source Extensions, in the browser itself, Apple includes that in the newer operating systems starting with Yosemite, and apparently they are not, or can't, upgrade Mavericks to include it. My hunch is that they didn't realize that YouTube would deactivate flash player for Safari 9, regardless of whether or not it had media source extensions in Mavericks. That's why they had first told me they were working with YouTube to resolve the problem, but apparently YouTube isn't doing anything to help, such as restoring the ability use to flash player if Media Source Extensions isn't available. Pretty amazing that between the two of these big companies they can't fix the problem.

On the other hand, Apple itself does not allow Flash player to be used on their videos in Safari 9, for example, video previews in the Apple Store, which have the same problem not showing 1080p.

Thanks a lot for taking the time to leave an update Red and Blue...!
I'm not surprised YouTube has chosen to leave their users eating dust, like they have already done before, even with presumably problematic issues like all those Smart TV, DV player and SetTop box Apps that one day just couldn't play YouTube any longer, through their officially licensed App on 3rd-party devices.
Kind of the same attitude they showed towards copyright infringement matters, leaving their users to the mercy of copyright infringement trolls, as covered in a recent Petapixel article: http://petapixel.com/2016/02/20/how-i-turned-a-bs-youtube-copyright-claim-back-o n-the-real-infringer/
I guess it's time for me to really make the effort and finally transition to Vimeo.

Thanks again,

Andy

Hello, I see Apple released Safari 9.1 for Mavericks 10.9.5 today. Anyone know if this fixes the You Tube HD resolution issue in Safari?

Thanks!!

I installed the update and no, it doesn't solve the problem with the HD in HTML5. Apple has told me they will never solve the problem. Unlike most browsers, the Media Source Extensions component of HTML5 is not in the browser itself, but in the operating system, and Apple will not or cannot update that in Mavericks. This is what YouTube says... I just noticed however the Firefox works in Mavericks 10.9.5 for me, although it has a lot of other issues so I don't use it regularly; manly, slow loading, slow, or almost nonexistent swiping back and forth, and problems with copy and paste. If I deactivate hardware acceleration in Firefox, as was suggested, it does improve the loading and swiping, but I noticed then that the video quality in HTML5 is terrible.

YouTube says:

Below are some browser and operating system combinations that support YouTube's high-quality video formats:

Google Chrome (all operating systems)

Internet Explorer or Edge on Windows 8.1 or newer

Safari on Mac OS X 10.10 or newer

Firefox on Windows 7 or newer and on Mac OS X 10.10 or newer

Well, since Apple says they will never fix the problem, I've decided to switch browsers to Chrome.

Thanks, Apple!

That's what I did ,switched to Chrome (Apple even suggested using another browser if one doesn't want to update--pretty unbelievable). I mainly use Safari if I want to upload something in one account while browsing in another account, and Firefox at times for some of the add-ons.