Here is how you resolve the error, ranked from most likely to least likely:

The most common cause is a previous driver session that didn't close properly, "locking" the local port.

driver.get("http://google.com") print(driver.title) driver.quit()

: If the default port is blocked, you can manually assign a port using FirefoxDriverService.CreateDefaultService().Port = 9222 .

Alternatively, use the using statement for automatic disposal:

or not found in default location.

: Occasionally, security software blocks the driver from opening a local socket. Temporarily disable your firewall to test if it's the culprit.

Ensure the FirefoxDriverService is pointing to the containing geckodriver.exe , not the executable file itself.

Download geckodriver.exe from GitHub mozilla/geckodriver . Move it to a folder like C:\WebDrivers\ and add that folder to your system PATH.

driver = webdriver.Firefox()

The system may not be able to find the driver, or it lacks permission to execute it. Stack Overflow to install Selenium.WebDriver.GeckoDriver . Ensure the property "Copy to Output Directory" geckodriver.exe "Copy if newer" Avoid running code from network/shared drives , as this can trigger permission errors. Google Groups 5. Binding Timeout

This error message (or variations of it) is one of the most common hurdles when setting up Selenium with Firefox in C#. It essentially means your C# code tried to launch the Firefox driver, but the driver process ( geckodriver.exe ) failed to start or crashed immediately.

If you're still facing this error, it would be helpful to know: What version of Firefox are you using? Are you using a proxy or a VPN? What does your code's initialization look like?