Windows 10: Reg File for Custom File Type Handler Program

  1.    04 Mar 2018 #1

    Reg File for Custom File Type Handler Program

    Suppose instead of the default reg settings for, say, pdf files, one wants a reg file to set up a custom program handler.

    For instance, Sumatra. One would like Sumatra to handle pdf files. When one double-clicks on a pdf file, Sumatra loads and shows the pdf file.

    How would one set up a reg file to establish that?

    As has been noted elsewhere, presently many are reporting that Windows seems to be switching our default program apps. So, in the pdf case, Sumatra is being switched to Edge. A reg file, then, to make the switch back would be greatly appreciated.

    One can then study the requested reg file to use with other switched extensions as well.

    Nicholas Kormanik
      My ComputerSystem Spec

  2.    04 Mar 2018 #2

    Welcome to the forum. Set pdf to sumatra then goto reg edit Computer\HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\ApplicationAssociationToasts find the key and export it then you have your reg file
      My ComputerSystem Spec

  3.    04 Mar 2018 #3

    Did as suggested. Saved entire registry branch:


    Rebooted computer.

    Instantly see what I'd earlier set up has been switched to what Microsoft wants. All reset.

    Then I merged the saved 'customized' branch back into registry. Hoping to get back to the associations that I want.

    No luck. Pdfs still load in Edge. As do epubs. Not Sumatra.
    And web links bring up Edge as well, instead of Chrome.

    Any other suggestions?

      My ComputerSystem Spec

  4.    05 Mar 2018 #4

    Click image for larger version. 

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    That's the one that changes if you change the association.
    You can try it for yourself- change the association e.g. via Open with and tick the box, then refresh the registry display.

    (The Openwithlist should (more or less) match those displayed when rt clicking a pdf and clicking Open with of course).

    Adobe users have historically been much more prone to pdf association problems. Not something I've seen much of personally.

    If attempting to make the change by merging a reg file, you may have to do more to apply the change.
      My ComputerSystem Spec

  5.    05 Mar 2018 #5

    Did you save the key for sumatra or the whole branch?
      My ComputerSystem Spec

  6.    05 Mar 2018 #6

    Feel free to tell me to butt out but I can't duplicate this behaviour. Using Win 10 Home 1709 Build 16299.125 x64 I installed SumatraPDF 3.1.2 using the Use SumatraPDF as the default PDF reader option:
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    After installation, the usual nonsense notification appeared:
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    I used Start > Settings > Apps > Default apps > Choose default applications by file type to select SumatraPDF for PDF files.

    Two restarts and a shutdown/restart later and the default PDF handler is still SumatraPDF.

    I reset the VM afterwards and did exactly the same again... with the exact same results. SumatraPDF remains the default PDF handler.
      My ComputerSystem Spec

  7.    05 Mar 2018 #7

    Hi, if you mean you don't find the default pdf handler reverting to Edge as described in post #1 I agree.

    However there are plenty of reports of this sort of thing, mostly related to the use of Adobe products. Older reports about unexpected changes to associations have occurred because of old versions of programs such as winzip being installed.
      My ComputerSystem Spec

  8.    05 Mar 2018 #8

    dalchina said:
    However there are plenty of reports of this sort of thing, mostly related to the use of Adobe products.
    Ah, thanks. I avoid Adobe products if I can, hence why I haven't seen the issue before. I was just interested in case this was another 'MS knows best for you' across the board. :)
      My ComputerSystem Spec

  9.    06 Mar 2018 #9

    Reg File for Custom File Type Handler Program

    After searching and experimenting like crazy, I finally found one solution that seems to work. 97% of the Windows program associations problem solved!

    Christoph Kolbicz is the wizard.


    Too complicated for me to explain. Go to his site and read about it.

    Thanks to all of you for helping.

    Nicholas Kormanik
      My ComputerSystem Spec


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