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I'm developing a Windows Forms app in C# using VS 2019. I've created a website with the download of the .exe file of my windows form app, but when I download it and I run it Microsoft Defender SmartScreen recognize the app as not safe.

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Is there a way to not show this warning when a person runs my app?

Dev
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    Except for **Craig T** answer there are two other possible way to remove the warning. The application must be recognized by many downloads (from many user) and not flagged as problematic. And second way is to **digitally sign the application** with a certificate by global certificate vendor. This will disable the warning from Windows. But even this method does not guarantees you that similar problem with some antivirus/security programs. – Julo Feb 27 '22 at 04:31
  • It is also a good idea to fill in all the fields in the project pane like author, company etc.. – TaW Feb 27 '22 at 08:48
  • If you find the solution, you could click '✔' to mark it as an answer to change its status to Answered. It will also help others to solve a similar issue. See also [stackoverflow.com/help/why-vote](https://stackoverflow.com/help/why-vote) – Jiale Xue - MSFT Feb 28 '22 at 02:01

2 Answers2

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According to Microsoft's documentation (https://learn.microsoft.com/en-us/windows/security/threat-protection/microsoft-defender-smartscreen/microsoft-defender-smartscreen-overview), they state that the following checks are done:

  1. Checking downloaded files against a list of reported malicious software sites and programs known to be unsafe. If it finds a match, Microsoft Defender SmartScreen shows a warning to let the user know that the site might be malicious.

  2. Checking downloaded files against a list of files that are well known and downloaded by many Windows users. If the file isn't on that list, Microsoft Defender SmartScreen shows a warning, advising caution.

Assuming your app hasn't been flagged as malcious software, it is most likely that SmartScreen warns users because Microsoft doesn't recognise it.

The link above provides advice on how to submit your application to Microsoft so it can be reviewed and added as an exception to SmartScreen.

Craig T
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It might be that it's not signed by Windows. I suppose when you release the app you should verify it with Microsoft, otherwise it will show the warning for any such app downloaded from the internet.

winwin
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