HTML 11 extension provides tool windows in Visual Studio 2017/2019 showing preview of an HTML document you are currently editing, on desktop and mobile devices:
The preview is updated as you type. When you change a .css or a .js file referenced in the HTML document, the preview is updated after you save the referenced file.
To initially open HTML 11 tool windows, select Desktop preview or Mobile preview in the main HTML11 menu:
You can position opened tool windows alongside the HTML editor or outside the main Visual Studio window, e.g. on a second monitor.
In HTML 11 options you can select a mobile device for preview:
HTML is rendered using Chromium Embedded Framework v75. A mobile device is simulated with Chromium DevTools Device Mode.