Cannot open json files in default app

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6

In your registry, .json's UserChoiceLatest is json_auto_file which points to notepad++.

Not sure why File Explorer isn't respecting that as well. Maybe the hash is wrong, so it's ignoring it, while we have no way to verify the hash as it's part of Microsoft's intentional obfuscation.

I'm also surprised if Open With > Choose Default App isn't changing UserChoiceLatest, on a system that has UserChoiceLatest at all. (This is all part of Microsoft's latest layer of undocumented changes to try and stop other software changing default applications like they do in their own apps. It's all very annoying. Some of the details may not yet be understood, and also seem to be changing as they test this new idea.)

HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts\.json\UserChoiceLatest\
HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts\.json\UserChoiceLatest: "Hash" is REG_SZ: "8PRmd9RkHAw="
HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts\.json\UserChoiceLatest\ProgId\
HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts\.json\UserChoiceLatest\ProgId: "ProgId" is REG_SZ: "json_auto_file"

HKCR\json_auto_file\
HKCR\json_auto_file\shell\
HKCR\json_auto_file\shell\open\
HKCR\json_auto_file\shell\open\command\
HKCR\json_auto_file\shell\open\command: "" is REG_SZ: ""C:\Program Files\Notepad++\notepad++.exe" "%1""

If regedit will allow you to delete this UserChoiceLatest registry key, things should work again:

  • HKEY_CURRENT_USER
    • Software
      • Microsoft
        • Windows
          • CurrentVersion
            • Explorer
              • FileExts
                • .json
                  • UserChoiceLatest

It may block you from deleting it, in which case the easiest workaround is to make an Opus-specific override. See Directory Opus opens PDF Files in Microsoft Edge instead of default PDF viewer - #24 by Leo for how to do that, as it's basically the same problem but with PDF instead of JSON.

So far only a few people have run into this problem, so it's probably something to do with Microsoft A/B testing different code/mechanisms at the moment.

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