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  1. I downloaded the insider version of Microsoft Edge (Version 79.0.309.25).
  2. Enabled ClickOnce: edge://flags/#edge-click-once
  3. Tried to start ClickOnce Application from a browser.

This has worked as expected on 4 computers now, but not my own computer (even though it works with the stable version of Edge 44.18362.449.0).

I can see from the developer tool's network tab that the request is sent, and the request/response headers looks the same as in stable Edge (except user-agent). The console gives me the following warning message which I suspect is (part) of the reason it does not work:

Resource interpreted as Document but transferred with MIME type application/x-ms-application: "_my_clickonce_url_".

UPDATE: Apparently this does show for working computers aswell, I was mistaken.

I do not get this message on the other computers that are working fine.

Searching for this message gives me alot of hits (but for other mime-types), for example:

They suggest fixes such as adding a download attribute to the link (which does not work in my case), or changing the returned content-type (which should be correct in my case). There seems to be some code related changes, but I suspect my issue is environmental since it only fails on one computer out of 5.

One answer also suggested to check the regestry editor for Computer\HKEY_CLASSES_ROOT\, but this also looks the same as other computer that works (.application maps to content type application/x-ms-application).

I suspect this might be more of a Microsoft support ticket than a stack overflow question, but I guess it depends on where the problem is. So I thought I'd start here.

running SystemInfo.exe in cmd gives following (large chunk redacted):

OS Name:                   Microsoft Windows 10 Enterprise
OS Version:                10.0.18362 N/A Build 18362
System Manufacturer:       Hewlett-Packard
System Model:              HP Z230 Tower Workstation
System Type:               x64-based PC
Hotfix(s):                 6 Hotfix(s) Installed.
                           [01]: KB4506991
                           [02]: KB4503308
                           [03]: KB4506472
                           [04]: KB4509096
                           [05]: KB4524569
                           [06]: KB4524570

Comparison of request headers of a working version:

:authority: _redacted_host_
:method: GET
:path: _path_/_AppName_.application?url=https://_redacted_host_:443/_redacted_endpoint_
:scheme: https
accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.9
accept-encoding: gzip, deflate, br
accept-language: en-US,en;q=0.9
referer: _redacted_url_
sec-fetch-mode: navigate
sec-fetch-site: same-origin
sec-fetch-user: ?1
upgrade-insecure-requests: 1
user-agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/79.0.3945.36 Safari/537.36 Edg/79.0.309.25

and a my non-working version:

:authority: _redacted_host_
:method: GET
:path: _path_/_AppName_.application?url=https://_redacted_host_:443/_redacted_endpoint_
:scheme: https
accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.9
accept-encoding: gzip, deflate, br
accept-language: sv,en;q=0.9,en-GB;q=0.8,en-US;q=0.7
referer: _redacted_url_
sec-fetch-mode: navigate
sec-fetch-site: same-origin
sec-fetch-user: ?1
upgrade-insecure-requests: 1
user-agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/79.0.3945.36 Safari/537.36 Edg/79.0.309.25

And as you can see, they are exactly the same except for the accept-language.

Update: Running Process Monitor (procmon.exe) and comparing results between working and non-working machine I find that the ClickOnce Launcher process (dfsvc.exe) never starts on my computer.

msedge.exe goes and checks the following registry key: HKCR\MIME\Database\Content Type\application/x-ms-application\Extension => ".application"

and then continues to find what seems to be the file extension handler: HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts\.application => "msedge.exe"

The non-working browser never reaches the second step.

micnil
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  • Did you check whether the machine on which it is working and your machine's configuration and settings are all similar or they has any difference? check whether you are using the same Windows update as other machines. Try to update the MS Edge Chromium browser if any new update is available. Try to reset the browser and again try to set the flags and make a test. Try to provide the steps which you follow to start the click once app. We will try to refer it and try to reproduce the issue for checking the results. – Deepak-MSFT Nov 19 '19 at 13:28
  • I really appreciate the help, but I find it really difficult to start comparing general system differences. Feels like I should start from the other direction, is there any logs in Edge that I can enable? What are the possible reasons to getting this warning? etc. But I have tried reinstalling edge, all computers use the same version of edge, but not the same version of Windows. I have tried clearing all browser caches and resetting the edge flags. During my troubleshooting I have also updated Windows, It did not work for me on version 1809 either (so Windows version might be unrelated). – micnil Nov 19 '19 at 14:33
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    I will try to discuss the issue and try to take the suggestions from senior engineer about this error. I will try to provide further suggestions as soon as I get any information. Thanks for your understanding. – Deepak-MSFT Nov 19 '19 at 14:59
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    I discussed the issue and it looks like something is related with your environment and engineer may need to check it for narrow down the issue. Their suggestion is to open a support ticket in Microsoft. thanks for your understanding. – Deepak-MSFT Nov 21 '19 at 07:53
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    `edge://flags/#edge-click-once` seems to be the best-kept secret of the new Edge. I wish it would come up in search results when trying to figure out why Edge no longer launched ClickOnce apps. – Fls'Zen Mar 03 '20 at 14:52

1 Answers1

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after long research, we found out, that this behavior sources in the smart screen filter.

if smartscreen is disabled, then it just won't work (with no error and no message). as soon as smartscreen is enabled, everything works as designed.

according to microsoft, this is by design and won't be changed (as large companies would ever allow smartscreen -.-)

Phil
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  • It's good, it's meant to force users to use the filter. Otherwise when someone downloads some malware without realizing it and it breaks their PC they might blame windows, and at times even switch to another OS. – Kitanga Nday May 05 '20 at 11:04
  • I have no longer any way to verify if this solves my problem (have switched job since question was asked). However, thanks a lot for updating it with your solution! :) – micnil May 05 '20 at 14:40