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Still can't? What is the deal with Apple? I have the same iMac and was looking forward to this update. I'm still testing things out on an old rMBP, and reading the forums to see if it's "safe" to update my iMac. So far, that would be a no. So dissapointing!
 
I can confirm that I cannot playback 4K Netflix on Safari on a 2020 iMac 5K running Big Sur 11.0.1. Also, I cannot playback 4K content on YouTube using Safari. This is supposed to be possible on Big Sur. See: https://9to5mac.com/2020/08/04/safari-in-big-sur-beta-4-4k-youtube-video-stream/
An interesting question that now arises is: Is the lack of 4K support in Netflix and/or YouTube in Safari in Big Sur because of lingering hardware DRM restrictions in the 2020 5k iMac, or is it because support was pulled from the stable release of Big Sur, regardless of hardware?
One way to get clarity is to see if a Mac that could playback 4K Netflix in Safari running one of the betas can still do so running the stable release.
The irony is the 5K iMac is one of the only Macs (the other being the iMac Pro) that can display the full 4K resolution on the internal display.
 
Just saw this in another thread. Apparently, this will help with YouTube. I haven't upgraded my iMac to Big Sur yet, so I can't test it. But it reportedly worked for someone. But for Netflix, I don't know.

\
Try - Developer menu - Experimental features - WP9 SW decoder on battery (on) - Web RTC WP9 codec (on).
 
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Just saw this in another thread. Apparently, this will help with YouTube. I haven't upgraded my iMac to Big Sur yet, so I can't test it. But it reportedly worked for someone. But for Netflix, I don't know.

\
Try - Developer menu - Experimental features - WP9 SW decoder on battery (on) - Web RTC WP9 codec (on).
Thanks. This worked for YouTube. Still not working for Netflix, though.
 
My Netflix its working. It just takes 30-60 secs for it to ramp up to that. It starts at 720, then goes up from there. This is a crummy photo of me playing Lost in Space in 4K. Didn't know what info is sensitive, so I redacted a little bit. Overly cautious, I guess. Anyway....
IMG_6443.jpeg
 
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My Netflix its working. It just takes 30-60 secs for it to ramp up to that. It starts at 720, then goes up from there. This is a crummy photo of me playing Lost in Space in 4K. Didn't know what info is sensitive, so I redacted a little bit. Overly cautious, I guess. Anyway....View attachment 1666837
may I ask what is you Safari > Develop > Experimental Feature setting please?
 
may I ask what is you Safari > Develop > Experimental Feature setting please?
There's a long list. I don't know what to give you. Sorry, this is the first time I've played around with this. I just followed what they said about "W9", but mine don't say W, they say "V". So I did that. I think that's just for YouTube though.

Are you subscribed to Netflix's top tier? Do you have a T2 in your Mac? I know those are requisites. Also, remember to let it play for a while. It really needs time to ramp up to that bitrate, depending on your internet speed.

1605388273855.png
 
My Netflix its working. It just takes 30-60 secs for it to ramp up to that. It starts at 720, then goes up from there. This is a crummy photo of me playing Lost in Space in 4K. Didn't know what info is sensitive, so I redacted a little bit. Overly cautious, I guess. Anyway....View attachment 1666837
Thank you. I can confirm that on my iMac it will ramp up to 4K after about 60-63 seconds.
 
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There's a long list. I don't know what to give you. Sorry, this is the first time I've played around with this. I just followed what they said about "W9", but mine don't say W, they say "V". So I did that. I think that's just for YouTube though.

Are you subscribed to Netflix's top tier? Do you have a T2 in your Mac? I know those are requisites. Also, remember to let it play for a while. It really needs time to ramp up to that bitrate, depending on your internet speed.

View attachment 1666857
I enabled WebRTC H265 codec as well.
 
There's a long list. I don't know what to give you. Sorry, this is the first time I've played around with this. I just followed what they said about "W9", but mine don't say W, they say "V". So I did that. I think that's just for YouTube though.

Are you subscribed to Netflix's top tier? Do you have a T2 in your Mac? I know those are requisites. Also, remember to let it play for a while. It really needs time to ramp up to that bitrate, depending on your internet speed.

View attachment 1666857
what about Safari > develop > user agent please?
 
There's a long list. I don't know what to give you. Sorry, this is the first time I've played around with this. I just followed what they said about "W9", but mine don't say W, they say "V". So I did that. I think that's just for YouTube though.

Are you subscribed to Netflix's top tier? Do you have a T2 in your Mac? I know those are requisites. Also, remember to let it play for a while. It really needs time to ramp up to that bitrate, depending on your internet speed.

View attachment 1666857
and how about the display setting? is it at default or scaled up or down?
 
and how about the display setting? is it at default or scaled up or down?
At this point, maybe call customer support. I'm trying to help as much as I can, but I don't really know as much as others around here do, and I'm kind of busy at the moment. But to answer your last question, "Default for display".

I didn't do anything magical. My iMac is pretty brand new. I've only had it for about 3 weeks, I think. I haven't messed with settings - except for the two Develop settings I referenced above. I only upgraded to BS this morning, so I haven't even explored everything. My first objective was to make sure I could play YouTube and Netflix at the higher rate. Now I've been able to do that.

Again, if you have a new Mac with a T2, and you are subscribed to Netflix UHD, and you updated the two items mentioned above, it should work. If it still isn't working, I'd call customer support. I wish you the best of luck.

Oh, and don't forget to give it time to ramp up. As Andy noted, it took his about 60 secs to get there. That's close to my experience.
 
@Canaan_c Same issue here. I have a Macbook Pro 2019 with T2 chip which can play 4k youtube videos, but Netflix still 1080p.
I found a different between I an @decypher44 is the codec. I am still using avchigh codec instead of hevc. That's why we can't stream 4k Netflix, but I still can't explain why.

Screen Shot 2020-11-15 at 11.33.41 AM.png
 
And now I got 4K netflix work by change user agent to: Mozilla/5.0 (Macintosh; Intel Mac OS X 11_0) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/14.0.1 Safari/605.1.15
Which "Intel Mac OS X 11_0" in final version is "Intel Mac OS X 10_15_6".
Screen Shot 2020-11-15 at 11.58.15 AM.png
 
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And now I got 4K netflix work by change user agent to: Mozilla/5.0 (Macintosh; Intel Mac OS X 11_0) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/14.0.1 Safari/605.1.15
Which "Intel Mac OS X 11_0" in final version is "Intel Mac OS X 10_15_6".View attachment 1667304
I changed to "Mozilla/5.0 (Macintosh; Intel Mac OS X 11_0) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/14.0.1 Safari/605.1.15"
the buffering bitrate still limited at 5800... no luck
 
At this point, maybe call customer support. I'm trying to help as much as I can, but I don't really know as much as others around here do, and I'm kind of busy at the moment. But to answer your last question, "Default for display".

I didn't do anything magical. My iMac is pretty brand new. I've only had it for about 3 weeks, I think. I haven't messed with settings - except for the two Develop settings I referenced above. I only upgraded to BS this morning, so I haven't even explored everything. My first objective was to make sure I could play YouTube and Netflix at the higher rate. Now I've been able to do that.

Again, if you have a new Mac with a T2, and you are subscribed to Netflix UHD, and you updated the two items mentioned above, it should work. If it still isn't working, I'd call customer support. I wish you the best of luck.

Oh, and don't forget to give it time to ramp up. As Andy noted, it took his about 60 secs to get there. That's close to my experience.
thanks, my iMac is 2020 T2 5700XT 27". I just dunno why it doesn't work..
but thanks for your help
 
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