Cannot Start The Driver Service On Http Localhost Selenium Firefox C Jun 2026
Sometimes the error occurs simply because Firefox is not installed or Selenium cannot locate the Firefox binary in the standard installation locations.
to isolate environmental factors
+--------------------+ (Fails to Start / Bind) +-------------------+ | Selenium C# Code | X--------------------------------> | geckodriver.exe | | (Local Client) | http://localhost:[port]/ | (Local Server) | +--------------------+ +-------------------+
Ensure Selenium is installed in the same environment where you run the script. Sometimes the error occurs simply because Firefox is
Some security software sees GeckoDriver opening a local port as suspicious behavior (like a reverse shell).
from selenium.webdriver.firefox.options import Options options = Options() options.binary_location = '/usr/bin/firefox' # or your Firefox path driver = webdriver.Firefox(options=options)
Have another strange Selenium error? Let me know in the comments! from selenium
If you are running your C# Selenium tests in a CI/CD pipeline (such as Azure DevOps, GitHub Actions, or Docker containers), the lack of a display monitor or specific environment arguments will cause the driver service to fail immediately.
driver.Url = "https://www.example.com"; // your test code here // driver.Quit() is called automatically
Incompatibility between the Selenium library, GeckoDriver, and the installed version of Firefox. driver
The manager might be downloading the wrong architecture (32-bit vs 64-bit) or failing to set up the service correctly.
System-wide proxy settings may interfere with localhost communication. Adding an environment variable NO_PROXY with the value localhost can bypass this.
FirefoxDriverService service = FirefoxDriverService.CreateDefaultService(); service.Host = "127.0.0.1"; // Force IPv4 explicitly var driver = new FirefoxDriver(service, new FirefoxOptions());
By default, Selenium tries to bind to localhost . If your local machine configuration maps localhost to an IPv6 address ( ::1 ) while the driver expects IPv4 ( 127.0.0.1 ), the service initialization will fail.
Technical Incident Report: Selenium WebDriver Initialization Error
