I tried that. I doesn't fix the issue for me. At 100% every app and interface element in Windows looks unreadably tiny. A 4k monitor typically has about 4 times as many pixels as a 1920 and therefore a scaling like 150% is more or less necessary. At that scaling almost every programs in Windows looks great, with sharp fonts and good size, except Mathematica.

If I use MM scaling as suggested (with Windows scaling at 100%), everything else in Windows is still tiny and many elements of Mathematica's interface (e.g. menu bar) are still tiny.

Thanks for the reply. I had already seen most of those links and they don't fix the issue. Is there an actual fix in any of them? When I tried their suggestions, they would improve some aspect but make others worse.

I noticed that in one of the suggested links, https://mathematica.stackexchange.com/questions/134054/blurry-fonts-in-notebooks it is stated:

UPDATE: Answer from a Wolfram Technology Engineer

Mathematica's front-end does not support 4K resolution monitors fully and is known to have some issues when used in 4K resolution monitors. Our developers are currently working on this issue.

I'm confused by this statement, as high-dpi displays have been mainstream for more than 5 years (e.g., MacBook Pro with Retina display). One of the 4k monitors I'm using has been out for more than 3 years.

As I said above:

"Also I am running mathematica 11.2 on my MacBook Pro (2012, Retina display, macOS Sierra 10.12.6), and there the OS has no problems, everything is perfect as it should be."

The problem is Mathematica on Windows with 4K Monitors!

I don't know how to make UI of Mathematica scales correctly and not blurry at the same time. But there are 2 good workarounds (probably mentioned in the links above):

(screenshots below are from my main/boot monitor, 3840x2160, DPI 200%)

1) Change DPI scaling behavior to "System (Enhanced)", and increase notebook "Magnification": Most part of UI looks sharp (except the notebook), and seems everything scales correctly.

2) Change DPI scaling behavior to "Application", and increase notebook "Magnification": Everything looks sharp, most parts of UI don't scale correctly but most contents of notebooks scale correctly.

Everything above 100%, doesn't matter if 200, 300 or something in between produces blurry fonts in Mathematica notebooks on Windows with 4k monitors.

What one can also try is to change the screen resolution in the mathematica preferences.

Attachments:

Thanks for the workarounds. They are not obvious at all. Workaround 2 is interesting, as it eliminates blurriness generally, though it leaves many things improperly scaled (e.g. the options inspector, searchbar in help, autocomplete). Items not scaled up are tiny in my laptop screen (which needs 200% Windows magnification). This means it is not really usable there, but might be usable in my external monitor at 150% Windows magnification.

There is no fix for this problem, but hopefully version 11.3 will make Mathematica support modern monitors.

It does not solved in version 11.3. It is disappointing.

No one will like this solution... I had a Dell 4k monitor and this affected too many applications on Windows 10, by chance I kept my Eizo 27" display with a native 2560 × 1440 resolution.. after a year I went back to the Eizo.

Problem solved.

I can say my 27" iMac with a 5k display does a much better job across the board for all applications.

The Dell 4K is on craigslist at a deep discount :)

I warned people. :)

Apple worked on HiDPI interfaces for years, I worked in the Core Graphics group while I was at Apple... it's not an easy challenge. You can take the naive approach and scale lower resolution content but thats really not enough because you end up with all the problems described. With LCD monitors you have to take into account a lot of edge information for RGB components of the LCD panel, layouts of glyphs and additional font information. Apple HiDPI actually works at a sub-pixel level to correct font placement for true type, which makes it look more accurate.

A typical 4k monitor display can actually display at 16k for 4x sampling, I know my Dell 4K monitor will display a 16k resolution but thats typically reserved for hardware oversampling a 4k resolution which just doesn't work for all situations well.

With 30 years in computer graphics my eye picks up all the errors and it just annoys me to no end to see these scaling issues, so I would rather live with a pixel accurate display than one that isn't.

To do it right the application has to render at the target resolution and not rely on naive scaling implementations between them and the user.