Add a web app manifest

Nov 5, 2018 • Updated Feb 25, 2021

Appears in: Progressive Web Apps

Pete LePage

François Beaufort

GitHub

Thomas Steiner

The web app manifest is a JSON file that tells the browser about your Progressive Web App and how it should behave when installed on the user's desktop or mobile device. A typical manifest file includes the app name, the icons the app should use, and the URL that should be opened when the app is launched.

Manifest files are supported in Chrome, Edge, Firefox, UC Browser, Opera, and the Samsung browser. Safari has partial support.

Create the manifest file

The manifest file can have any name, but is commonly named manifest.json and served from the root (your website's top-level directory). The specification suggests the extension should be .webmanifest, but browsers also support .json extensions, which is may be easier for developers to understand.

{
  "short_name": "Weather",
  "name": "Weather: Do I need an umbrella?",
  "icons": [
    {
      "src": "/images/icons-192.png",
      "type": "image/png",
      "sizes": "192x192"
    },
    {
      "src": "/images/icons-512.png",
      "type": "image/png",
      "sizes": "512x512"
    }
  ],
  "start_url": "/?source=pwa",
  "background_color": "#3367D6",
  "display": "standalone",
  "scope": "/",
  "theme_color": "#3367D6",
  "shortcuts": [
    {
      "name": "How's weather today?",
      "short_name": "Today",
      "description": "View weather information for today",
      "url": "/today?source=pwa",
      "icons": [{ "src": "/images/today.png", "sizes": "192x192" }]
    },
    {
      "name": "How's weather tomorrow?",
      "short_name": "Tomorrow",
      "description": "View weather information for tomorrow",
      "url": "/tomorrow?source=pwa",
      "icons": [{ "src": "/images/tomorrow.png", "sizes": "192x192" }]
    }
  ],
  "description": "Weather forecast information",
  "screenshots": [
    {
      "src": "/images/screenshot1.png",
      "type": "image/png",
      "sizes": "540x720"
    },
    {
      "src": "/images/screenshot2.jpg",
      "type": "image/jpg",
      "sizes": "540x720"
    }
  ]
}

Key manifest properties

`short_name` and/or `name`

You must provide at least the short_name or name property. If both are provided, short_name is used on the user's home screen, launcher, or other places where space may be limited. name is used when the app is installed.

`icons`

When a user installs your PWA, you can define a set of icons for the browser to use on the home screen, app launcher, task switcher, splash screen, and so on.

The icons property is an array of image objects. Each object must include the src, a sizes property, and the type of image. To use maskable icons, sometimes referred to as adaptive icons on Android, you'll also need to add "purpose": "any maskable" to the icon property.

For Chrome, you must provide at least a 192x192 pixel icon, and a 512x512 pixel icon. If only those two icon sizes are provided, Chrome will automatically scale the icons to fit the device. If you'd prefer to scale your own icons, and adjust them for pixel-perfection, provide icons in increments of 48dp.

`start_url`

The start_url is required and tells the browser where your application should start when it is launched, and prevents the app from starting on whatever page the user was on when they added your app to their home screen.

Your start_url should direct the user straight into your app, rather than a product landing page. Think about what the user will want to do once they open your app, and place them there.

`background_color`

The background_color property is used on the splash screen when the application is first launched on mobile.

`display`

You can customize what browser UI is shown when your app is launched. For example, you can hide the address bar and browser chrome. Games can even be made to launch full screen.

Property	Use
`fullscreen`	Opens the web application without any browser UI and takes up the entirety of the available display area.
`standalone`	Opens the web app to look and feel like a standalone app. The app runs in its own window, separate from the browser, and hides standard browser UI elements like the URL bar.
`minimal-ui`	This mode is similar to `standalone`, but provides the user a minimal set of UI elements for controlling navigation (such as back and reload).
`browser`	A standard browser experience.

`display_override`

Web apps can choose how they are displayed by setting a display mode in their manifest as explained above. Browsers are not required to support all display modes, but they are required to support the spec-defined fallback chain ("fullscreen" → "standalone" → "minimal-ui" → "browser"). If they don't support a given mode, they fall back to the next display mode in the chain. This inflexible behavior can be problematic in rare cases, for example, a developer cannot request "minimal-ui" without being forced back into the "browser" display mode when "minimal-ui" is not supported. Another problem is that the current behavior makes it impossible to introduce new display modes in a backward compatible way, since explorations like tabbed application mode don't have a natural place in the fallback chain.

These problems are solved by the display_override property, which the browser considers before the display property. Its value is a sequence of strings that are considered in the listed order, and the first supported display mode is applied. If none are supported, the browser falls back to evaluating the display field.

In the example below, the display mode fallback chain would be as follows. (The details of "window-control-overlay" are out-of-scope for this article.)

"window-control-overlay" (First, look at display_override.)
"minimal-ui"
"standalone" (When display_override is exhausted, evaluate display.)
"minimal-ui" (Finally, use the display fallback chain.)
"browser"

{
  "display_override": ["window-control-overlay", "minimal-ui"],
  "display": "standalone",
}

The browser will not consider display_override unless display is also present.

`scope`

The scope defines the set of URLs that the browser considers to be within your app, and is used to decide when the user has left the app. The scope controls the URL structure that encompasses all the entry and exit points in your web app. Your start_url must reside within the scope.

Caution: If the user clicks a link in your app that navigates outside of the scope, the link will open and render within the existing PWA window. If you want the link to open in a browser tab, you must add target="_blank" to the <a> tag. On Android, links with target="_blank" will open in a Chrome Custom Tab.

A few other notes on scope:

If you don't include a scope in your manifest, then the default implied scope is the directory that your web app manifest is served from.
The scope attribute can be a relative path (../), or any higher level path (/) which would allow for an increase in coverage of navigations in your web app.
The start_url must be in the scope.
The start_url is relative to the path defined in the scope attribute.
A start_url starting with / will always be the root of the origin.

`theme_color`

The theme_color sets the color of the tool bar, and may be reflected in the app's preview in task switchers. The theme_color should match the meta theme color specified in your document head.

`shortcuts`

The shortcuts property is an array of app shortcut objects whose goal is to provide quick access to key tasks within your app. Each member is a dictionary that contains at least a name and a url.

`description`

The description property describes the purpose of your app.

`screenshots`

The screenshots property is an array of image objects, representing your app in common usage scenarios. Each object must include the src, a sizes property, and the type of image.

In Chrome, the image must respond to certain criteria:

Width and height must be at least 320px and at most 3840px.
The maximum dimension can't be twice larger than the minimum dimension.
Screenshots must have the same aspect ratio.
Only JPEG and PNG image formats are supported.

Gotchas!

The description and screenshots properties are currently used only in Chrome for Android when a user wants to install your app. The experimental flag chrome://flags/#mobile-pwa-install-use-bottom-sheet flag must be enabled in Chrome 90.

Add the web app manifest to your pages

After creating the manifest, add a <link> tag to all the pages of your Progressive Web App. For example:

<link rel="manifest" href="/manifest.json">

Gotchas!

The request for the manifest is made without credentials (even if it's on the same domain), thus if the manifest requires credentials, you must include crossorigin="use-credentials" in the manifest tag.

Test your manifest

To verify your manifest is setup correctly, use the Manifest pane in the Application panel of Chrome DevTools.

The application panel in Chrome Devtools with the manifest tab selected.

This pane provides a human-readable version of many of your manifest's properties, and makes it easy to verify that all of the images are loading properly.

Splash screens on mobile

When your app first launches on mobile, it can take a moment for the browser to spin up, and the initial content to begin rendering. Instead of showing a white screen that may look to the user like the app is stalled, the browser will show a splash screen until the first paint.

Chrome automatically creates the splash screen from the manifest properties, specifically:

name
background_color
icons

The background_color should be the same color as the load page, to provide a smooth transition from the splash screen to your app.

Chrome will choose the icon that closely matches the device resolution for the device. Providing 192px and 512px icons is sufficient for most cases, but you can provide additional icons for pixel perfection.