Cannot Start The Driver Service On Http Localhost Selenium Firefox C 【VERIFIED × 2027】

Another service is using the same port on localhost , or firewall rules are blocking the communication.

Cannot Start the Driver Service on http localhost Selenium Firefox C#

Solution: Add an inbound and outbound rule in your Windows Firewall to allow geckodriver.exe full communication privileges on your local network. 5. Define the Exact Firefox Binary Path

pip install --upgrade selenium

Before we fix it, we must understand it.

The most reliable way to avoid the error is to let a manager handle binaries.

If you frequently stop your test executions abruptly via the IDE (e.g., stopping the Visual Studio debugger mid-test), the driver.Quit() method is bypassed. This leaves orphan geckodriver.exe and firefox.exe processes running invisibly in the background. Eventually, these processes can lock up system resources or conflict with new port allocations. Another service is using the same port on

(Chrome/Chromedriver) to isolate if issue is Firefox‑specific.

The error "" in Selenium C# typically occurs when the geckodriver executable fails to launch or communicate within the expected timeframe. Common Fixes

taskkill /F /IM geckodriver.exe /T taskkill /F /IM firefox.exe /T Use code with caution. Clean Implementation Template Define the Exact Firefox Binary Path pip install

chmod +x /path/to/geckodriver

(Python example):

If this server fails to spin up or bind to a port on localhost , Selenium throws this exception. The breakdown below details why this handshake fails. This leaves orphan geckodriver