Window Controls Overlay API

Limited availability

This feature is not Baseline because it does not work in some of the most widely-used browsers.

Experimental:This is anexperimental technology
Check theBrowser compatibility table carefully before using this in production.

The Window Controls Overlay API gives Progressive Web Apps installed on desktop operating systems the ability to hide the default window title bar and display their own contentover the full surface area of the app window, turning the control buttons (maximize, minimize, and close) into an overlay.

Opting-in to the feature

Before using this feature, the following conditions must be true:

The Web App Manifest'sdisplay_override member must be set towindow-controls-overlay.
The Progressive Web App must be installed on a desktop operating system.

Main concepts

Progressive Web Apps installed on desktop devices can be displayed in standalone app windows, just like native apps. Here is what an application window looks like:

Illustration of a PWA installed on desktop, with window control buttons, a title bar, and web content below that

As seen above, the app window is made of two main areas:

The title bar area at the top.
The application content area at the bottom, which displays the HTML content from the PWA.

The title bar area contains the system-critical maximize, minimize, and close buttons (their position may vary across operating systems), the name of the application (which comes from the<title> HTML element in the page), and possibly user-agent-specific PWA buttons.

With the Window Controls Overlay feature, Progressive Web Apps can display their web content over the whole app window surface area. Because the window control buttons and user-agent-specific PWA buttons must remain visible, they get turned into an overlay displayed on top of the web content.

Illustration of a PWA installed on desktop with the Window Controls Overlay feature, with window control buttons, no title bar, and web content spanning the whole window

The part of the title bar that normally contains the application name is hidden, and the area that it normally occupies becomes available via the Window Controls Overlay API.

PWAs can use the API to position content in this area, and avoid having content hidden behind the control buttons overlay, similar to how web authors can account for the presence of notches on certain mobile devices.

CSS environment variables

Progressive Web Apps can position their web content in the area that the title bar normally occupies by using thetitlebar-area-x,titlebar-area-y,titlebar-area-width, andtitlebar-area-height CSS environment variables.SeeUsing env() to ensure content is not obscured by window control buttons in desktop PWAs.

Interfaces

WindowControlsOverlayExperimental: Provides information about the visibility and geometry of the title bar and an event to know whenever it changes.
WindowControlsOverlayGeometryChangeEventExperimental: Represents events providing information related to the desktop Progress Web App's title var region when its size or visibility changes.

Extensions to other interfaces

Navigator.windowControlsOverlay: Returns theWindowControlsOverlay interface, which exposes information about the title bar geometry in desktop Progressive Web Apps.