Definition

Web App Manifest

Short definition

A Web App Manifest is a JSON file (usually manifest.webmanifest) that declares your app's name, icons, start URL, theme colour and display mode. The browser reads it to render the install prompt and the home-screen icon.

Reviewed July 8, 2026

The manifest is served from any URL on the origin and linked from the page head with <link rel="manifest" href="/manifest.webmanifest">.

Chromium refuses the install prompt when the manifest is missing required fields — at minimum name (or short_name), a 512px icon, start_url and a display value of standalone or fullscreen.

iOS Safari uses the manifest for name and theme colour, but home-screen icon still requires <link rel="apple-touch-icon"> at 180x180.

Related terms

Service worker

A service worker is a JavaScript file the browser runs in the background, separate from the page. It intercepts network requests, caches responses so the site works offline, and receives web-push events so the site can notify the user when it is closed.

beforeinstallprompt

beforeinstallprompt is a window event Chromium browsers fire when a site meets the PWA install criteria. Capturing the event and calling prompt() later lets you show the install dialog at a moment of your choosing instead of at page load.

Standalone display mode

Standalone is a value of the display field in a Web App Manifest. It tells the browser to launch the PWA in its own window with no address bar or tabs, so it looks and behaves like a native app. It is the most common display mode for installable PWAs.