How to set the size of a browser window using Selenium?

driver.manage().window().maximize();

System.out.println(driver.manage().window().getSize());
// Output: (1024, 768)

import org.openqa.selenium.Dimension;

Dimension d = new Dimension(1280, 800);
driver.manage().window().setSize(d);

// Verify
System.out.println(driver.manage().window().getSize());
// Output: (1280, 800)

import org.openqa.selenium.Point;

driver.manage().window().setPosition(new Point(0, 0));  // Top-left corner

driver.manage().window().fullscreen();

// Mobile viewport
Dimension mobile = new Dimension(375, 812);  // iPhone X
driver.manage().window().setSize(mobile);

// Tablet viewport
Dimension tablet = new Dimension(768, 1024);  // iPad
driver.manage().window().setSize(tablet);

// Desktop
Dimension desktop = new Dimension(1920, 1080);  // Full HD
driver.manage().window().setSize(desktop);

JavascriptExecutor js = (JavascriptExecutor) driver;
js.executeScript("window.resizeTo(1280, 800);");

@BeforeClass
public void setup() {
    driver = new ChromeDriver();
    driver.manage().window().maximize();
    // OR for responsive testing:
    // driver.manage().window().setSize(new Dimension(375, 812));
}