determine default browser setting in a WinUI app in Windows11

Question

I followed several hints on how to get the "default browser" in windows, but they all are how to read the registry path from Current.User: Software\Microsoft\Windows\Shell\Associations\UrlAssociations\http\UserChoice

HOWEVER, I have both Chrome and Edge on my machine. When switching between the two as the default, I always get "ChromeHTML". So, this does not seem like it will work!

This happens to be for a .NET MAUI app

Are you referring to the ProgId value? What do you see under HKEY_CLASSES_ROOT\ChromeHTML ? — Dai
– Dai, Commented Sep 20 at 2:14
@Dai, whether Chrome or Edge is set as default, this shows info about Chrome. — bobwki
– bobwki, Commented Sep 22 at 16:27

Andrew KeepCoding · Accepted Answer · 2025-09-22 01:43:59Z

1

This works on Windows 11:

internal static bool TryGetSystemDefaultBrowserPath(out string path)
{
    path = string.Empty;

    try
    {
        using var regDefault = Registry.CurrentUser.OpenSubKey(
            name: "Software\\Microsoft\\Windows\\CurrentVersion\\Explorer\\FileExts\\.htm\\UserChoice",
            writable: false);

        if (regDefault?.GetValue("ProgId") is not string { Length: > 0 } stringDefault)
        {
            return false;
        }

        using var regKey = Registry.ClassesRoot.OpenSubKey(
            name: stringDefault + "\\shell\\open\\command",
            writable: false);

        if (regKey?.GetValue(null) is not string raw ||
            string.IsNullOrWhiteSpace(raw))
        {
            return false;
        }

        var name = raw.Trim().Trim('"');

        var exeIndex = name.IndexOf(".exe", StringComparison.OrdinalIgnoreCase);

        if (exeIndex < 0)
        {
            return false;
        }

        name = name[..(exeIndex + 4)];
        path = name;
        return true;
    }
    catch
    {
        return false;
    }
}

answered Sep 22 at 1:43

Andrew KeepCoding

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5 Comments

Andrew KeepCoding Sep 23 at 0:04

@bobwki You've set the bounty after I posted this answer. Does that mean that this answer didn't solve your issue?

bobwki Sep 29 at 18:59

well, on my system it always returned "ChromeHTML", whether set to Chrome or Edge. So, no. I appreciated your answer, though, so I upvoted.

Andrew KeepCoding Sep 29 at 20:26

This method returns the "path" to the default browser. Can you check again?

bobwki Oct 2 at 16:06

I tried again today, and, maddeningly, when I changed default browser to Edge, and restarted Windows, and verified by using the Windows Search box to open my website, your call still returns CHROME -- C:\Program Files\Google\Chrome\Application\chrome.exe. Hard to believe...

bobwki Oct 2 at 16:23

EVEN MORE MADDENING -- I uninstalled Chrome. Now your code returns "false". "stringDefault" is set to "ChromeHTML", which leads to the next OpenSubKey to return NULL.

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