The Web App Manifest
Define PWA metadata with a manifest.json file.
What a Manifest Does
A web app manifest is a JSON file that tells the browser how to install the page as an app: which name to use, which icon to display, which URL to launch, what color scheme to apply, and which display mode to render in (standalone, fullscreen, browser).
Linking the Manifest
Reference the manifest from every page that should be installable: <link rel="manifest" href="/manifest.webmanifest"> in the head. The browser fetches it once and caches it; updates to the manifest are picked up on subsequent loads.
<link rel="manifest" href="/manifest.webmanifest">