Window Management API

Historically, we have used Window.open() to manage browser windows related to the current application — opening new windows, resizing and closing existing windows, etc. For example, to open a 400×300 window 50 pixels from the left and top of your screen:

const myWindow = window.open(
  "https://example.com/",
  "myWindow",
  "left=50,top=50,width=400,height=300",
);

You can retrieve information about your screen from the Window.screen property, such as how much screen space you have available to place windows in.

However, the above features are limited. Window.screen only returns data about the primary screen, and not secondary displays available to a device. To move a window to a secondary display, you could use Window.moveTo(), but you'd have to guess what coordinates to use based on where it is placed in your setup relative to the primary display.

The Window Management API provides more robust, flexible window management. It allows you to query whether your display is extended with multiple screens and get information on each screen separately: windows can then be placed on each screen as desired. It also provides event handlers to allow you to respond to changes in the available screens, new fullscreen functionality to choose which screen to put into fullscreen mode (if any), and permissions functionality to control access to the API.

For details on how to use it, see Using the Window Management API.

The Window Management API is useful in cases such as:

• Multi-window graphics editors and audio processors that may wish to arrange editing tools and panels across different screens.
• Virtual trading desks that want to show market trends in multiple windows and put specific windows of interest in fullscreen mode.
• Slideshow apps that want to show speaker notes on the internal primary screen and the presentation on an external projector.

The window-management Permissions-Policy can be used to control permission to use the Window Management API. Specifically:

• Usage of the Window.getScreenDetails() method. If blocked, its Promise will reject with a NotAllowedError exception.
• Querying the Window.screen.isExtended property. If blocked, it will always return false.

Developers can explicitly grant permission for an <iframe> to use Window Management via the allow attribute:

<iframe src="3rd-party.example" allow="window-management"></iframe>

ScreenDetails Secure context

Represents the details of all the screens available to the user's device.

ScreenDetailed Secure context

Represents detailed information about one specific screen available to the user's device.

The Screen change event Secure context

Fired on a specific screen when it changes in some way — for example available width or height, or orientation.

Screen.isExtended Secure context

A boolean property that returns true if the user's device has multiple screens, and false if not.

Element.requestFullscreen(), the screen option

Specifies on which screen you want to put the element in fullscreen mode.

Window.getScreenDetails() Secure context

Returns a Promise that fulfills with a ScreenDetails object instance.

You can find full examples here:

• Basic multi-window learning environment (see the source code).
• Multi-window Platformer Game (see the source code).
• Elmer-inspired trading desk demo (see the source code).
• Window placement demo (see the source code).