 André Cipriani Bandarra [X](https://twitter.com/andreban) [GitHub](https://github.com/andreban) [Mastodon](https://mastodon.social/@andreban) [Bluesky](https://bsky.app/profile/bandarra.me) [Homepage](https://bandarra.me)
> [!NOTE]
> **Note:** If you are new to Trusted Web Activities, you may want to read the [Trusted Web Activity Quick Start Guide](https://developer.chrome.com/docs/android/trusted-web-activity/quick-start.md.txt) or the [Introduction to Trusted Web Activities](https://developer.chrome.com/docs/android/trusted-web-activity.md.txt) before reading this documentation.
**Trusted Web Activities** are a new way to integrate your web-app content such as your PWA with
your Android app using a protocol based on Custom Tabs.
A Trusted Web Activity needs the origins being opened to be validated using
[Digital Asset Links](https://developers.google.com/digital-asset-links), in order to show the content in full-screen.
When a user navigates off the validated origin, Custom Tab UI is shown. The URL bar in the Custom
Tab tells the users they are now navigating in a domain outside the application, while also
providing the user with an X button that allows them to quickly return to the validated origin.
But it is also common for Web Apps to create experiences that span multiple origins - An example
would be a shopping application with the main experience at *www.example.com* , while the checkout
flow is hosted at *checkout.example.com*.
In cases like that, showing the Custom Tabs is undesirable, not only because the user is in the
same application, but also because the top bar could make the user think they left the application
and abandon the checkout.
Trusted Web Activities allow developers to validate multiple origins, and the user will remain in
full-screen when navigating across those origins. As with the main domain, the developer must be
able to control each validated origin.
## Setting up validation for multiple origins
As in the main origin, the validation is achieved via Digital Asset Links and each domain to be
validated needs to have its own assetlinks.json file.
### Add an assetlinks file to each origin
In our example with *www.example.com* and *checkout.example.com*, we would have:
- `https://www.example.com/.well-known/assetlinks.json`
- `https://checkout.example.com/.well-known/assetlinks.json`
Since each domain is getting connected to the same Android application, the `assetlinks.json` files
look exactly the same.
Assuming the package name for the Android application is `com.example.twa`, both `assetlink.json`
files would contain something similar to the following:
```json
[{
"relation": ["delegate_permission/common.handle_all_urls"],
"target": {
"namespace": "android_app",
"package_name": "com.example",
"sha256_cert_fingerprints": ["..."]}
}]
```
> [!NOTE]
> **Note:** An application using Trusted Web Activities can have any number of validated domains, as long as Digital Asset Links are implemented for all of them.
### Add multiple origins to the Android Application
On the Android application, the `asset_statements` declaration needs to be updated to contain all
origins that need to be validated:
```xml
[{
\"relation\": [\"delegate_permission/common.handle_all_urls\"],
\"target\": {
\"namespace\": \"web\",
\"site\": \"https://www.example.com\"
}
}],
[{
\"relation\": [\"delegate_permission/common.handle_all_urls\"],
\"target\": {
\"namespace\": \"web\",
\"site\": \"https://checkout.example.com\"
}
}],
```
> [!NOTE]
> **Note:** Applications based on the [svgomg-twa demo](https://github.com/GoogleChromeLabs/svgomg-twa) application or [bubblewrap](https://github.com/GoogleChromeLabs/bubblewrap) have the `asset_statements` declaration inside `app/build.gradle`. Even though the location of the declaration is different, the JSON content is the same.
## Add extra origins to the LauncherActivity
### Using the default LauncherActivity
The [`LauncherActivity`](https://github.com/GoogleChrome/android-browser-helper/blob/master/androidbrowserhelper/src/main/java/com/google/androidbrowserhelper/trusted/LauncherActivity.java) that is part of the [`android-browser-helper`](https://github.com/GoogleChrome/android-browser-helper/) support library
provides a way to add multiple origins to be validated by configuring the Android project.
First, add a `string-array` element to the `res/values/strings.xml` file. Each extra URL to be
validated will be inside an `item` sub-element:
```xml
...
- https://www.google.com
...
```
Next, add a new `meta-data` tag inside the existing activity element that references the
`LauncherActivity`, inside `AndroidManifest.xml`:
```xml
...
...
...
```
## Using a custom LauncherActivity
When using custom code to launch a Trusted Web Activity, adding extra origins can be achieved by
calling `setAdditionalTrustedOrigins` when building the Intent to launch the Trusted Web Activity:
```java
public void launcherWithMultipleOrigins(View view) {
List origins = Arrays.asList(
"https://checkout.example.com/"
);
TrustedWebActivityIntentBuilder builder = new TrustedWebActivityIntentBuilder(LAUNCH_URI)
.setAdditionalTrustedOrigins(origins);
new TwaLauncher(this).launch(builder, null, null);
}
```
## Conclusion
With those steps, the Trusted Web Activity is now ready to support multiple origins.
android-browser-helper has a [sample application](https://github.com/GoogleChrome/android-browser-helper/tree/master/demos/twa-multi-domain) for multi origin Trusted Web Activities. Make
sure to check it.
## Troubleshooting
Setting up Digital Asset Links has a few moving parts. If the application is still showing the
Custom Tabs bar on the top, it's likely that something is wrong with the configuration.
The [Trusted Web Activity Quick Start Guide](https://developer.chrome.com/docs/android/trusted-web-activity/quick-start.md.txt) has a great [troubleshooting section](https://developer.chrome.com/docs/android/trusted-web-activity/quick-start.md.txt#troubleshooting) on how to
debug Digital Asset Link issues.
There's also the amazing [Peter's Asset Link Tool](https://play.google.com/store/apps/details?id=dev.conn.assetlinkstool), which helps debuggint Digital Asset Links
on applications installed on the device..