In a multi-monitor display environment, how do I tell Selenium which display to open a new window in?

Two options (this is for the coypu c# wrapper):

1. Use the Selenium Driver's window positioning commands:

   var monitor = Screen.FromPoint(new Point(Screen.PrimaryScreen.Bounds.Right + 1, Screen.PrimaryScreen.Bounds.Top));
   
   var seleniumDriver = new ChromeDriver(options);
   seleniumDriver.Manage().Window.Position = new Point(monitor.Bounds.X, monitor.Bounds.Y);
   
   var coypuDriver = new MultimonWebDriver(seleniumDriver, Browser.Chrome);
   var rv = new BrowserSession(sessionConfiguration, coypuDriver);
   

2. Configure the Driver with a command line argument. I prefer this because solution #1 causes a flicker from the driver's server showing the window before processing the move command:

   var monitor = Screen.FromPoint(new Point(Screen.PrimaryScreen.Bounds.Right + 1, Screen.PrimaryScreen.Bounds.Top));
   
   var options = new ChromeOptions();
   options.AddArgument(String.Format("--window-position={0},{1}", monitor.Bounds.X, monitor.Bounds.Y));
   
   var seleniumDriver = new ChromeDriver(options);
   var coypuDriver = new MultimonWebDriver(seleniumDriver, Browser.Chrome);
   var rv = new BrowserSession(sessionConfiguration, coypuDriver);
   

where MultimonWebDriver is simply exposing access to the protected constructor:

public class MultimonWebDriver : SeleniumWebDriver
{
  public MultimonWebDriver(IWebDriver webDriver, Browser browser) : base(webDriver, browser)
  {
  }
}

In python:

browser = webdriver.Chrome()
browser.set_window_position(2000, 0)

In OSX Mavericks you can assign desktop from the Options menu when clicking and holding the icon from the dock. This solved the problem for me.