Cannot Start The Driver Service On Http Localhost Selenium Firefox C [new] 🎉

The good news is that with Selenium 4.6 and later, much of this complexity has been abstracted away. The Selenium Manager automatically handles driver downloads, version matching, and service initialization. If you're able to upgrade to the latest Selenium version, you'll find that this particular error becomes increasingly rare.

Open Task Manager and end all geckodriver.exe tasks. The good news is that with Selenium 4

Ensure that Firefox is installed in a standard location: Open Task Manager and end all geckodriver

If you're an automation engineer working with Selenium WebDriver in C#, you've likely encountered this frustrating exception at some point: Try running your IDE (Visual Studio, JetBrains Rider)

FirefoxDriverService service = FirefoxDriverService.CreateDefaultService(); service.LogPath = @"C:\temp\geckodriver.log"; // Save logs to file var driver = new FirefoxDriver(service, new FirefoxOptions());

Ensure you have the latest release from the official Mozilla GitHub repository.

On restrictive enterprise machines, the driver executable may lack the necessary Windows permissions to spawn a new subprocess. Try running your IDE (Visual Studio, JetBrains Rider) or your command line console as an Administrator.