Fiddler Ideas

The free web debugging proxy for any browser, system or platform.

4k font scaling not working on Windows 10

I'm using v5.0.20181.13826 for .NET 4.6.1.  I just upgraded today.  I have a 4k display running at 3840 x 2160.  I have the font scaling set to 200%.  The previous version of Fiddler worked with these settings.  I accepted the update when prompted today, but the Fiddler UI is no longer scaling the font.  Many of the menus are inaccessible or unusable.  

I set my resolution to 1920 x 1080 with no scaling and the Fiddler UI was accessible.  I was able to access the menus and set the Fiddler font to 16, and returned to my regular 4k display settings.  Most of Fiddler was readable under this setting, but several areas don't appear to acknowledge this change.  Screen shots attached.  

  • Chris Swanski
  • Mar 15 2018
  • Shipped
  • Attach files
  • Johann Dirry commented
    March 15, 2018 13:17

    The GUI is now unuseable on a high res display. using a Surface Tablet with default settings.

  • Paul Martin commented
    March 15, 2018 14:38

    I'm seeing the exact same issue. I then added the -dpiAware switch to the shortcut which helped some but parts of the app are still displaying wonky. See screenshot.

  • Alan Clelland commented
    March 15, 2018 15:23


    I'm seeing the same issue on my 4k monitor but I'm also seeing Fiddler become very blurry when moving the window to my second monitor which is 1920x1080 so I'm unable to use this latest version on either monitor.




  • Taylor Wallgren commented
    March 15, 2018 15:30

    My resolution is 2560x1440 and the text is way smaller than it used to be (difficult for me to read) and the menu bar's text is cut off. 

  • None now commented
    March 15, 2018 15:51

    Fonts too small, menu text scrunched/partially displayed. Not useable on all displays that we have tried.

  • Some One commented
    March 15, 2018 16:13

    Also using a Surface Pro 4 with scaling set to 175% (default is 200%).  It is unusable.  I set scaling to 100% to test if it is just scaling that is ignored but dialogs and menus are still a complete mess.

  • Daren May commented
    March 15, 2018 18:20

    This issue is disastrous - how do I roll back?

  • Jamin Peckham commented
    March 15, 2018 18:23

    Same thing here with 2560x1440 resolution. Font sizes are all over the place.

  • Tsviatko Yovtchev commented
    March 15, 2018 19:15

    What version did you guys update from? We haven't really changed anything UI related in the new release. It has to be some change in Windows I guess. I could provide an old version of Fiddler to test that theory. I just have to know which one.

  • Alan Clelland commented
    March 15, 2018 19:29

    It was a fairly recent version, I last updated about a month ago. Is there
    a log which might include the version number I upgraded from?

  • Taylor Wallgren commented
    March 15, 2018 19:34

    I had version 4.6.20173.38786 which I downloaded back in September. I updated it today after a popup let me know there was a new version.

  • Darren Kopp commented
    March 15, 2018 19:35

    Not sure what my previous version was, but my new version is v5.0.20181.13826

  • Darren Kopp commented
    March 15, 2018 19:46

    I did install windows updates last night, but the Fiddler UI looked normal and prompted me to update, and it was messed up after the update.

  • Raffaele Rialdi commented
    March 15, 2018 20:20

    The problems relies in the high-dpi awareness of Fiddler.

    A temporary workaround is to suppress Fiddler high-dpi management going into the Fiddler.exe file properties:

    • Compatibility Tab
    • Check the option: "Override high DPI scaling behavior"
    • in the combo box specify: "System"

    In any case something has definitely changed in Fiddler or Windows since it never happened before.
    The test must be done with high-dpi monitors and specifying a magnification > 100% (e.g. 150%)


  • Ilya Kulshin commented
    March 15, 2018 21:15

    Re: Tsviatko Yovtchev: just updated today. Not sure what previous version I was using, but I have autoupdates enabled and I was using fiddler earlier this week without having been prompted for an update. I assume the previous version worked.

  • Guest commented
    March 16, 2018 02:24

    I'm seeing the exact same issue. Hope be fixed asap.

  • Tsviatko Yovtchev commented
    March 16, 2018 12:27

    We are not able to reproduce the problem to its full extent locally. So, it would be really nice if you guys could help us a bit further. Here are the six previous public versions of Fiddler. What would help us is:

    1. What is the resolution of the monitor where Fiddler exhibits this problem?
    2. Are there other monitors on the system? What are their resolutions?
    3. What is the full Windows version?
    4. What is the most recent .NET version installed?
    5. Does any of the previous Fiddler versions behave differently? Which one?
  • Chris Swanski commented
    March 16, 2018 12:31

    I rolled back to my previously installed version of v4.6.20173.38786 and the issues does not present itself.

  • Tsviatko Yovtchev commented
    March 16, 2018 12:34

    And least but not least

    6. Are you running Fiddler with the -dpiaware parameter or not?

  • Andrew Freese commented
    March 16, 2018 14:21

    This isn't a windows update problem. Fiddler was working today until I upgraded. the -dpiAware flag DOES make fiddler usable again but it's kind of messy. See attached. BTW: i did NOT use dpiAware on old version.


    1) 4K
    2) Yes. Same. Same DPI and font scaling
    3) win 10 pro 1709 build 16299.192
    4) 4.6.1 (i think)
    5) Yes. Prev version was fine. I update when the UI tells me to.
    6) Yes. Makes it usable but still donked up a bit.

  • Jamin Peckham commented
    March 16, 2018 14:25

    I installed the below version and no issues.

    v5.0.20173.50948 for .NET 4.6.1
    Built: Thursday, December 14, 2017

    64-bit AMD64, VM: 46.0mb, WS: 92.0mb
    .NET 4.6.2 WinNT 10.0.16299.0

    DPI setting to 125% in Windows

    I let it auto update to v5.0.20181.13826 and the issue immediately came back.

    Using the -dpiaware flag fixed it!

  • Jamin Peckham commented
    March 16, 2018 14:53

    A few more interesting observations. 

    The current and previous release both have the same behavior when using -dpiaware flag. I'm seeing that with a larger font set under appearance, text gets clipped inside the elements - looks ugly but works. The previous version v5.0.20173.50948 handles text size changes without the -dpiaware flag much better.

    My primary monitor is at 2560x1440. Secondary (laptop screen) is at 1920x1080. DPI at 125%

    v5.0.20173.50948 for .NET 4.6.1
    Built: Thursday, December 14, 2017

    64-bit AMD64, VM: 43.0mb, WS: 85.0mb
    .NET 4.6.2 WinNT 10.0.16299.0

  • Darren Kopp commented
    March 16, 2018 19:53

    Installing v5.0.20173.50948 fixes the issue for me without having to do anything with -dpiAware. -dpiAware did improve the latest version, but there were still slight issues where tabs seemed too short in height.


    1. Resolution 2880 x 1800, scaling = 200%
    2. No
    3. 10.1709.16299.309
    4. .NET Framework 4.7.1
    5. Yes. 5.0.20173.50948

  • Sam Dso commented
    March 19, 2018 00:04

    I want to go back to previous version. How do I do that? This is terrible.

  • Demon Lin commented
    March 19, 2018 02:32

    Open the Fiddler.exe Properties window, switch to the compatibility panel and find system enhanced DPI zoom to resolve

  • Guest commented
    March 20, 2018 18:17

    Just got the latest update (v5.0.20181.14850). The UI is better but is still a bit blurry when viewed at 150% on my 4K.

  • Kurt commented
    March 26, 2018 06:59

    Latest update worked a treat for me! Thanks!