If it works, add an exception for geckodriver.exe in your Windows Defender or Antivirus settings. 4. Clean Up Hanging Processes
Since GeckoDriver starts a local web server to communicate with your code, firewalls might flag it as "unauthorized network activity." Temporarily disable your firewall to test.
If a previous debug session crashed, a "ghost" instance of GeckoDriver might still be holding onto the port. Open . End all tasks named geckodriver.exe . End all tasks named firefox.exe . 📋 Best Practices for C#
Cannot Start The Driver Service On Http Localhost Selenium Firefox C May 2026
If it works, add an exception for geckodriver.exe in your Windows Defender or Antivirus settings. 4. Clean Up Hanging Processes
Since GeckoDriver starts a local web server to communicate with your code, firewalls might flag it as "unauthorized network activity." Temporarily disable your firewall to test. If it works, add an exception for geckodriver
If a previous debug session crashed, a "ghost" instance of GeckoDriver might still be holding onto the port. Open . End all tasks named geckodriver.exe . End all tasks named firefox.exe . 📋 Best Practices for C# If it works