Cannot Start The Driver Service On Http Localhost Selenium Firefox C

from selenium import webdriver from selenium.webdriver.firefox.service import Service

(port 4444 or a random port is blocked).

Alternatively, run this in CMD (admin): taskkill /F /IM geckodriver.exe /T .

from selenium import webdriver from selenium.webdriver.firefox.service import Service from selenium import webdriver from selenium

Incompatibility between Firefox, GeckoDriver, and Selenium versions.

service = Service(executable_path='geckodriver.exe', port=9999) driver = webdriver.Firefox(service=service)

Running into OpenQA.Selenium.WebDriverException: 'Cannot start the driver service on http://localhost:XXXXX/' while using and C# ? This usually means the driver service failed to launch or your code is misconfigured. Here are the most effective ways to fix it: 1. Kill Lingering Processes service = Service(executable_path='geckodriver

Open the Task Manager (Ctrl + Shift + Esc), find geckodriver.exe or firefox.exe in the list, and select End Task .

The exception OpenQA.Selenium.WebDriverException: 'Cannot start the driver service on http://localhost:[port]/' is a frustrating roadblock for C# automation engineers. It happens right at initialization when . Because the local HTTP server wrapper for the driver cannot boot up, Selenium halts before your code even reaches the browser.

service = Service('/opt/homebrew/bin/geckodriver') # example macOS path driver = webdriver.Firefox(service=service) Kill Lingering Processes Open the Task Manager (Ctrl

Before diving into solutions, it's important to understand what's happening behind the scenes. When you instantiate a FirefoxDriver in your C# test:

dotnet add package Selenium.WebDriver dotnet add package Selenium.WebDriver.GeckoDriver Use code with caution.

The error is a common headache for C# developers using Selenium with Firefox. It typically means the GeckoDriver executable is unable to establish a local network connection to start its internal server. 🛠️ Root Causes Port Conflicts: Another process is using the default port. Loopback Issues: localhost isn't resolving to 127.0.0.1 .

Benefits: