Cannot Start The Driver Service On | Http Localhost Selenium Firefox C

Based on extensive community reports and official Selenium documentation, the following are the primary reasons for this error when working with Firefox in C#.

The most frequent cause is too many background driver processes hanging and blocking ports.

This error frequently appears in CI/CD environments where test agents lack proper configuration. Here are targeted solutions for pipeline environments: Based on extensive community reports and official Selenium

geckodriver --version

If you still face the issue after following this guide, check the exact stack trace for clues like "Connection refused" (firewall) or "Permission denied" (Unix file modes). When in doubt, restart your machine, reinstall both Firefox and GeckoDriver, and run the minimal script as a standard (non-admin) user. On Windows with mixed IPv4 and IPv6 networking

The most frequent cause is a firewall or VPN blocking the communication between your script and the Stack Overflow Temporarily disable your

c# - 'Cannot start the driver service on http://localhost:60681/' restart your machine

A VPN or system proxy is preventing communication with localhost .

On Windows with mixed IPv4 and IPv6 networking (the default for most systems), .NET Core attempts to resolve “localhost” to the IPv6 address ::1 first. If that fails, it retries on 127.0.0.1 after about a one-second delay. This delay can cause timeouts with Firefox (though not typically with Chrome, Edge, or IE).