Based on extensive community reports and official Selenium documentation, the following are the primary reasons for this error when working with Firefox in C#.
Outdated drivers frequently crash upon startup. Modern versions of Selenium 4 feature an internal that automatically downloads the matching GeckoDriver for your Firefox browser version. To ensure everything is up to date:
Selenium has no built-in "search" for GeckoDriver. If you don't tell it exactly where the executable is, it fails silently and throws this cryptic localhost error.
Resolving "Cannot start the driver service on http://localhost" in Selenium Firefox (C#) Based on extensive community reports and official Selenium
Before we fix it, we must understand it.
c# - 'Cannot start the driver service on http://localhost:60681/'
When developing automation scripts using , encountering the OpenQA.Selenium.WebDriverException: 'Cannot start the driver service on http://localhost:XXXXX/' error can bring your entire testing workflow to a screeching halt. This specific exception indicates that the Selenium C# bindings failed to launch the local geckodriver.exe process or failed to establish an HTTP handshake connection with it on the assigned localhost port. To ensure everything is up to date: Selenium
Using port=7055 often resolves conflicts because it's a reserved port for WebDriver.
Some security software sees GeckoDriver opening a local port as suspicious behavior (like a reverse shell).
If multiple microservices face this issue, add a machine-wide bypass rule: Press Win + R , type sysdm.cpl , and hit . c# - 'Cannot start the driver service on
service = Service(executable_path='/path/to/geckodriver') driver = webdriver.Firefox(service=service)
The system cannot find the geckodriver.exe file. 1. Match Your Versions
// Now initialize the driver IWebDriver driver = new FirefoxDriver();
System-level proxies or active VPNs sometimes prevent Selenium from communicating with localhost .