When you build a Web project, Unity embeds the Player in a HTML page such that a browser can open it. A Web template is a configuration setting that lets you control the appearance of this HTML page, so that you can test, demonstrate, and preview your Web application in a browser.
To access Web templates:
By default, the Web Template setting has the following options:
These built-in HTML pages are useful for testing and demonstrating a minimal Player.
You can also use JavaScript to build and supply your own Web templates to host the Player. This is useful for production purposes, so that you can preview the Player hosted in the page where it’s deployed. For example, if the Unity Player content interacts with other elements in the page via the external call interface, test it with a page that contains those interacting elements.