Control how your app is launched.
The Launch Handler API lets you control how your app is launched, for example, whether it uses an
existing or a new window and whether the chosen window is navigated to the launch URL. As with
the File Handing API, this also enqueues a LaunchParams
object in the launched page's window.launchQueue
.
Current status
Step | Status |
---|---|
1. Create explainer | Complete |
2. Create initial draft of specification | Complete |
3. Gather feedback & iterate on design | Complete |
4. Origin trial. | Complete |
5. Launch | Complete |
Using the Launch Handler API
Browser support
Launch Handler is only available on ChromeOS.
Interfaces
The Launch Handler API defines two new interfaces.
LaunchParams
: An object containing the targetURL
to be handled by the consumer.
LaunchQueue
: Queues launches until they are handled by the specified consumer.
The launch_handler
manifest member
To declaratively specify the launch behavior of your app, add the launch_handler
manifest member
to your manifest. It has one sub-field called client_mode
. It lets you control whether a new or an
existing client should be launched and if this client should be navigated. The example
below shows a file with exemplary values that would always route all launches to a new
client.
{
"launch_handler": {
"client_mode": "navigate-new"
}
}
If unspecified, launch_handler
defaults to {"client_mode": "auto"}
. The allowed values for the
sub-fields are:
client_mode
:navigate-new
: A new browsing context is created in a web app window to load the launch's target URL.navigate-existing
: The most recently interacted with browsing context in a web app window is navigated to the launch's target URL.focus-existing
: The most recently interacted with browsing context in a web app window is chosen to handle the launch. A newLaunchParams
object with itstargetURL
set to the launch URL will be enqueued in the document'swindow.launchQueue
.auto
: The behavior is up to the user agent to decide what works best for the platform. For example, mobile devices only support single clients and would useexisting-client
, while desktop devices support multiple windows and would usenavigate-new
to avoid data loss.
The client_mode
property also accepts a list (array) of values, where the first valid value will be
used. This is to allow new values to be added to the spec without breaking backwards compatibility
with existing implementations.
For example, if the hypothetical value "focus-matching-url"
were added, sites would specify
"client_mode": ["focus-matching-url", "navigate-existing"]
to continue to control the
behavior of older browsers that did not support "focus-matching-url"
.
Using window.launchQueue
In the following code, the function extractSongID()
extracts a songID
from the URL
passed on launch. This is used to play a song in a music player PWA.
if ('launchQueue' in window) {
launchQueue.setConsumer((launchParams) => {
if (launchParams.targetURL) {
const songID = extractSongId(launchParams.targetURL);
if (songID) {
playSong(songID);
}
}
});
}
Demo
You can see a demo of the Launch Handler API in action in the PWA Launch Handler Demo. Be sure to check out the source code of the application to see how it uses the Launch Handler API.
- Install the Musicr 2.0 app on a ChromeOS device.
- Send yourself a link in a chat application of the form
https://launch-handler.glitch.me?track=https://example.com/music.mp3
. (You can customizehttps://example.com/music.mp3
for any URL pointing to an audio file, for example,https://launch-handler.glitch.me?track=https://cdn.glitch.me/3e952c9c-4d6d-4de4-9873-23cf976b422e%2Ffile_example_MP3_700KB.mp3?v=1638795977190
). - Click the link in your chat app and notice how Musicr 2.0 opens and plays the track.
- Click the link in your chat app again and notice that you will not get a second instance of Musicr 2.0.
Feedback
The Chromium team wants to hear about your experiences with the Launch Handler API.
Tell us about the API design
Is there something about the API that does not work like you expected? Or are there missing methods or properties that you need to implement your idea? Have a question or comment on the security model? File a spec issue on the corresponding GitHub repo, or add your thoughts to an existing issue.
Report a problem with the implementation
Did you find a bug with Chromium's implementation? Or is the implementation different from the spec?
File a bug at new.crbug.com. Be sure to include as much detail as you can,
simple instructions for reproducing, and enter Blink>AppManifest
in the Components box.
Glitch works great for sharing quick and easy repros.
Show support for the API
Are you planning to use the Launch Handler API? Your public support helps the Chromium team prioritize features and shows other browser vendors how critical it is to support them.
Send a tweet to @ChromiumDev using the hashtag
#LaunchHandler
and
let us know where and how you are using it.