What's the Difference Between screenX/Y, clientX/Y, and pageX/Y in Web Development?

Understanding ScreenX/Y, ClientX/Y, and PageX/Y

In the realm of web development, understanding the differences between screenX/Y, clientX/Y, and pageX/Y is crucial for precise navigation and positioning elements on the page.

Defining the Coordinates

• pageX/Y: Coordinates relative to the entire rendered page, including areas hidden by scrolling.
• clientX/Y: Coordinates relative to the visible portion of the page within the browser window.
• screenX/Y: Coordinates relative to the physical screen.

Example of Usage

Consider a web page with its content extending beyond the viewport. When a user scrolls down, the pageY and pageX values will still represent the position of the mouse cursor relative to the entire page. However, the clientX and clientY values will update to reflect the position within the visible area.

iPad Safari Considerations

For iPad Safari, the viewport is smaller than the physical screen. Therefore, the clientX/Y and pageX/Y coordinates will differ from the screenX/Y coordinates.

Demo and Code Snippet

To illustrate these differences, you can visit the provided demo or execute the following JavaScript snippet:

document.addEventListener('DOMContentLoaded', () => {
  const info = document.getElementById('info');
  const updateInfo = event => {
    const { clientX, clientY, pageX, pageY } = event;
    info.innerHTML = `clientX: ${clientX} clientY: ${clientY}<br />pageX: ${pageX} pageY: ${pageY}`;
  };
  document.addEventListener('mouseover', updateInfo);
  document.addEventListener('mousemove', updateInfo);
});

This snippet demonstrates the dynamic update of coordinates as the mouse moves over and scrolls the page.

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