How do I set browser width and height in Selenium WebDriver?

Here is how I do it in Python with Selenium 2.48.0:

from selenium.webdriver import Firefox
driver = Firefox()
driver.set_window_position(0, 0)
driver.set_window_size(1024, 768)

For me, the only thing that worked in Java 7 on OS X 10.9 was this:

// driver = new RemoteWebDriver(new URL(grid), capability);
driver.manage().window().setPosition(new Point(0,0));
driver.manage().window().setSize(new Dimension(1024,768));

Where 1024 is the width, and 768 is the height.

Here's a solution that works with both headless and non-headless mode and will start the window with the specified size instead of setting it after:

Chrome:

from selenium.webdriver import Chrome
from selenium.webdriver.chrome.options import Options

opts = Options()
opts.add_argument("--window-size=2560,1440")

driver = Chrome(options=opts)

Firefox:

from selenium.webdriver import Firefox, FirefoxOptions

opts = FirefoxOptions()
opts.add_argument("--width=2560")
opts.add_argument("--height=1440")

driver = Firefox(options=opts)

Try something like this:

IWebDriver _driver = new FirefoxDriver();
_driver.Manage().Window.Position = new Point(0, 0);
_driver.Manage().Window.Size = new Size(1024, 768);

Not sure if it'll resize after being launched though, so maybe it's not what you want

If you are using chrome

 chrome_options = Options()
 chrome_options.add_argument("--start-maximized");
 chrome_options.add_argument("--window-position=1367,0");
 if mobile_emulation :
     chrome_options.add_experimental_option("mobileEmulation", mobile_emulation)

  self.driver = webdriver.Chrome('/path/to/chromedriver', 
                                  chrome_options = chrome_options)

This will result in the browser starting up on the second monitor without any annoying flicker or movements across the screen.