share_target

The value of the share_target member is an object that defines how an application can receive shared data. This object may contain the following properties (action and params are required):

action

The URL for the web share target.

enctype Optional

The encoding of the share data when a POST request is used. Ignored with GET requests.

method Optional

The HTTP request method to use. Either GET or POST. Use POST if the shared data includes binary data like image(s), or if it changes the target app, for example, if it creates a data point like a bookmark.

params

An object to configure the share parameters. The object keys correspond to the data object in navigator.share(). The object values can be specified and will be used as query parameters:

• title Optional: Name of the query parameter to use for the title of the document being shared.
• text Optional: Name of the query parameter for the text (or body) of the message being shared.
• url Optional: Name of the query parameter for the URL to the resource being shared.
• files Optional: An object (or an array of objects) defining which files are accepted by the share target. The object requires the following properties:
  • name: Name of the form field used to share files.
  • accept: A string (or an array of strings) of accepted MIME types or file extensions.

A share target can be registered using the following share_target manifest member:

{
  "share_target": {
    "action": "/shared-content-receiver/",
    "method": "GET",
    "params": {
      "title": "name",
      "text": "description",
      "url": "link"
    }
  }
}

When a user selects your app in the system's share dialog, your PWA is launched, and a GET HTTP request is made to the provided URL including the specified query parameters. It will look like this: /shared-content-receiver/?name=a+shared+name&description=a+shared+description&link=https%3A%2F%2Fexample.com%2F.

The URLSearchParams interface can be useful to handle the shared data in your application and do something with it.

const sharedName = url.searchParams.get("name");
const sharedDescription = url.searchParams.get("description");
const sharedLink = url.searchParams.get("link");

If the share request includes one or multiple files or causes a side effect in your application, the HTTP POST method should be used. For example, if your application receives images for further processing or wants to save a shared link as a bookmark in your database.

{
  "share_target": {
    "action": "/save-bookmark/",
    "method": "POST",
    "enctype": "multipart/form-data",
    "params": {
      "url": "link"
    }
  }
}

You can either handle POST share data using server-side code, or, to provide a better experience for offline users, a fetch event listener can be used to intercept the HTTP request which allows to access the data in a service worker.

self.addEventListener("fetch", (event) => {
  // Regular requests not related to Web Share Target.
  if (event.request.method !== "POST") {
    event.respondWith(fetch(event.request));
    return;
  }

  // Requests related to Web Share Target.
  event.respondWith(
    (async () => {
      const formData = await event.request.formData();
      const link = formData.get("link") || "";
      // Instead of the original URL `/save-bookmark/`, redirect
      // the user to a URL returned by the `saveBookmark()`
      // function, for example, `/`.
      const responseUrl = await saveBookmark(link);
      return Response.redirect(responseUrl, 303);
    })(),
  );
});

The POST request is then ideally replied with an HTTP 303 See Other redirect to avoid multiple POST requests from being submitted if a page refresh was initiated by the user, for example.

To accept shared files, the HTTP method must be POST, the enctype must be multipart/form-data, and a files entry defining the types of accepted files must be provided.

Files must have a name property, and the accept property must specify accepted MIME types or file extensions. It's probably a good idea to define both, since operating systems might differ in which they prefer.

{
  "share_target": {
    "action": "/file-collector",
    "method": "POST",
    "enctype": "multipart/form-data",
    "params": {
      "title": "name",
      "text": "description",
      "url": "link",
      "files": [
        {
          "name": "lists",
          "accept": ["text/csv", ".csv"]
        },
        {
          "name": "photos",
          "accept": ["image/svg+xml", ".svg"]
        }
      ]
    }
  }
}

To handle shared file data, see the POST example above and the FileReader API to read the files. In order to get the files from the service worker context over to client contexts, one solution is to temporarily write the files to the Cache or IndexedDB and then notify its clients using Client.postMessage().

Your PWA can only act as a web share target if it has been installed. See also How to make PWAs installable.

Similar to HTML form submissions, you should be cautious about data that is sent to your application via the share target. Be sure to validate incoming data before using it.