Cannot Start The Driver Service On Http Localhost Selenium Firefox C 🆕 Fully Tested

Selenium cannot find the executable that launches Firefox.

Solution:

from selenium import webdriver
from selenium.webdriver.firefox.service import Service
service = Service(executable_path=r'C:\WebDrivers\geckodriver.exe')
driver = webdriver.Firefox(service=service)

If you are automating web tests with Selenium in C#, few things are as frustrating as setting up your environment, writing your first script, hitting "Run," and being greeted by a critical red exception:

OpenQA.Selenium.DriverServiceNotFoundException: Cannot start the driver service on http://localhost:XXXXX/

Or perhaps you are seeing:

OpenQA.Selenium.WebDriverException: Cannot start the driver service on http://localhost:4444/

This error is the bane of many Selenium developers, particularly those working with the Firefox browser in a C# .NET environment. It essentially means your C# code tried to knock on the door of the GeckoDriver application, but nobody answered.

In this deep dive, we will explore exactly why this happens and, more importantly, how to fix it. We will cover the common pitfalls, the Path variable issues, and the modern solution using NuGet packages. Selenium cannot find the executable that launches Firefox

service = Service(port=7056)  # default is 7055

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

driver = webdriver.Firefox(options=options)