Add a web app manifest
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, among other things.
Manifest files are supported in most browsers though support for individual members may vary quite a bit.
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 may be easier for developers to understand.
A typical manifest looks something like this:
{
"short_name": "Weather",
"name": "Weather: Do I need an umbrella?",
"icons": [
{
"src": "/images/icons-vector.svg",
"type": "image/svg+xml",
"sizes": "512x512"
},
{
"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 Chromium, you must provide at least a 192x192 pixel icon, and a 512x512 pixel icon. If only those two icon sizes are provided, Chrome automatically scales 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 user interface elements. Games can even be made to launch full screen. The display property takes one of the following values:
| 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 such as 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.
Consider the example below. (The details of "window-control-overlay" are out-of-scope for this article.)
{
"display_override": ["window-control-overlay", "minimal-ui"],
"display": "standalone",
}As stated, the browser will look at display_override first.
"window-control-overlay""minimal-ui"
If neither option is available, it falls back to display. If "standalone" is not available, it resumes spec-defined fallabck chain from that point.
"standalone""minimal-ui""browser"
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.
A few other notes on scope:
- If you don't include a
scopein your manifest, then the default impliedscopeis the directory that your web app manifest is served from. - The
scopeattribute 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_urlmust be in the scope. - The
start_urlis relative to the path defined in thescopeattribute. - A
start_urlstarting 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.
As of Chromium 93 and Safari 15, you can adjust this color in a media query with the media attribute of the meta theme color element. The first one that matches will be picked. For example, you could have one color for light mode and another one for dark mode. At the time of writing, you can't define those in your manifest. See w3c/manifest#975 GitHub issue.
<meta name="theme-color" media="(prefers-color-scheme: light)" content="white">
<meta name="theme-color" media="(prefers-color-scheme: dark)" content="black">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 more than 2.3 times as long as the minimum dimension.
- All screenshots must have the same aspect ratio.
- Only JPEG and PNG image formats are supported.
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">Test your manifest #
To verify your manifest is setup correctly, use the Manifest pane in the Application panel of Chrome DevTools.
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:
namebackground_coloricons
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.
Further reading #
There are several additional properties that can be added to the web app manifest. Refer to the MDN Web App Manifest documentation for more information.