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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
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  • Guest commented
    26 Mar, 2018 06:59am

    Latest update worked a treat for me! Thanks!

  • Guest commented
    20 Mar, 2018 06:17pm

    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.

  • Demon Lin commented
    19 Mar, 2018 02:32am

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

  • Guest commented
    19 Mar, 2018 12:04am

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

  • Guest commented
    16 Mar, 2018 07:53pm

    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

  • Jamin Peckham commented
    16 Mar, 2018 02:53pm

    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

  • Jamin Peckham commented
    16 Mar, 2018 02:25pm

    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!

  • Andrew Freese commented
    16 Mar, 2018 02:21pm

    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.

  • Deleted User commented
    16 Mar, 2018 12:34pm

    And least but not least

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

  • Chris Swanski commented
    16 Mar, 2018 12:31pm

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

  • Deleted User commented
    16 Mar, 2018 12:27pm

    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?
  • Guest commented
    16 Mar, 2018 02:24am

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

  • Guest commented
    15 Mar, 2018 09:15pm

    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.

  • Raffaele Rialdi commented
    15 Mar, 2018 08:20pm

    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%)


  • Guest commented
    15 Mar, 2018 07:46pm

    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.

  • Guest commented
    15 Mar, 2018 07:35pm

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

  • Taylor Wallgren commented
    15 Mar, 2018 07:34pm

    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.

  • Alan Clelland commented
    15 Mar, 2018 07:29pm

    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?

  • Deleted User commented
    15 Mar, 2018 07:15pm

    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.

  • Jamin Peckham commented
    15 Mar, 2018 06:23pm

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

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