SOLVED - How to open a URL in the default browser in c#

For launching a URL in the default browser, I used to write this simple c# code:


But during my tests today I got a nice exception when i execute this code:


System.ComponentModel.Win32Exception was unhandled
Message=The system cannot find the file specified
 at System.Diagnostics.Process.StartWithShellExecuteEx(ProcessStartInfo startInfo)
 at System.Diagnostics.Process.Start()
 at System.Diagnostics.Process.Start(ProcessStartInfo startInfo)
 at System.Diagnostics.Process.Start(String fileName)
 at ConsoleApplication6.Program.Main(String[] args) in c:\Users\michaelseirer\Documents\Visual Studio 2013\Projects\ConsoleApplication6\ConsoleApplication6\Program.cs:line 20

Now, it seems that this code in previous versions of Windows worked. And the reason, why it is not working on my system is simply because I have Chrome as my default browser... (the code works with Firefox as default browser)

Setting it back to IE solved the problem:

But: who wants this? ... ;)


So I googled a bit and found code, that reads the path to the current default browser in the Registry in HKEY_CLASSES_ROOT\http:

But - lo and behold! - the subtree does not change if you change to another default browser. This registry-place seems to be a dead end (it maybe was used in earlier versions of Windows?) This is also mentioned here in this thread at a Microsoft forum.


The Solution

Starting with Windows Vista a new "Default Programs" was introduced. In this case, the value a user can set his own choice of browser (per user, not per machine!) - and it will be saved under the following registry key: 


There, you can find a string that identifies the browser:

  • FirefoxURL - for Firefox
  • ChromeHTML - for Chrome
  • IE.HTTP - for Internet Explorer
  • and probably some more (but I have not tested others)

The value here is a pointer to HKEY_CLASSES_ROOT\<Name> , e.g. HKEY_CLASSES_ROOT\IE.HTTP. The concrete starting path to the executable can be found here: HKEY_CLASSES_ROOT\<name>\shell\open\command 


This led to the following - though in my opinion huge amount of code - to actually launch a Url in the default browser:

public static string GetDefaultBrowserPath()
string urlAssociation = @”Software\Microsoft\Windows\Shell\Associations\UrlAssociations\http”;
string browserPathKey = @”$BROWSER$\shell\open\command”;

RegistryKey userChoiceKey = null;
string browserPath = “”;

//Read default browser path from userChoiceLKey
userChoiceKey = Registry.CurrentUser.OpenSubKey(urlAssociation + @”\UserChoice”, false);

//If user choice was not found, try machine default
if (userChoiceKey == null)
//Read default browser path from Win XP registry key
var browserKey = Registry.ClassesRoot.OpenSubKey(@”HTTP\shell\open\command”, false);

//If browser path wasn’t found, try Win Vista (and newer) registry key
if (browserKey == null)
browserKey =
urlAssociation, false);
var path = CleanifyBrowserPath(browserKey.GetValue(null) as string);
return path;
// user defined browser choice was found
string progId = (userChoiceKey.GetValue(“ProgId”).ToString());

// now look up the path of the executable
string concreteBrowserKey = browserPathKey.Replace(“$BROWSER$”, progId);
var kp = Registry.ClassesRoot.OpenSubKey(concreteBrowserKey, false);
browserPath = CleanifyBrowserPath(kp.GetValue(null) as string);
return browserPath;
catch(Exception ex)
return “”;

This way, you open the URL in the browser the user actually specified (or that is configured system-wide - depending on the OS).


Process.Start(GetDefaultBrowserPath(), url);


These have been the resources I found useful during my research and that helped me gathering the function above:



REMARK 06/11/15:

After updating to the latest Google Chrome version (in my case I updated from 35.0.1916.114 to 35.0.1916.153) Process.Start worked also for Google Chrome. So it seems that only some versions of Chrome had this issue.






Posted on June 11, 2014 and filed under development, Windows 8.