Selenium doesn't talk to the Firefox browser directly. It acts as a middleman. Your C# code sends a command to a separate executable called . This executable acts as a server, listening for commands on a specific port (usually on localhost).
Before we fix it, we must understand it. Selenium doesn't talk to the Firefox browser directly
This error is Selenium’s way of saying: “I tried to launch Firefox, but the bridge (GeckoDriver) connecting me to the browser collapsed before the connection could be established.” Selenium doesn't talk to the Firefox browser directly