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Linking

Linking gives you a general interface to interact with both incoming and outgoing app links.

Every Link (URL) has a URL Scheme, some websites are prefixed with https:// or http:// and the http is the URL Scheme. Let's call it scheme for short.

In addition to https, you're likely also familiar with the mailto scheme. When you open a link with the mailto scheme, your operating system will open an installed mail application. Similarly, there are schemes for making phone calls and sending SMS. Read more about built-in URL schemes below.

Like using the mailto scheme, it's possible to link to other applications by using custom url schemes. For example, when you get a Magic Link email from Slack, the Launch Slack button is an anchor tag with an href that looks something like: slack://secret/magic-login/other-secret. Like with Slack, you can tell the operating system that you want to handle a custom scheme. When the Slack app opens, it receives the URL that was used to open it. This is often referred to as deep linking. Read more about how to get the deep link into your app.

Custom URL scheme isn't the only way to open your application on mobile. You don't want to use a custom URL scheme in links in the email because then the links would be broken on desktop. Instead, you want to use a regular https links such as https://www.myapp.io/records/1234546. and on mobile you want that link open your app. Android calls it Deep Links (Universal Links - iOS).

Built-in URL Schemes​

As mentioned in the introduction, there are some URL schemes for core functionality that exist on every platform. The following is a non-exhaustive list, but covers the most commonly used schemes.

SchemeDescriptioniOSAndroid
mailtoOpen mail app, eg: mailto: support@expo.io✅✅
telOpen phone app, eg: tel:+123456789✅✅
smsOpen SMS app, eg: sms:+123456789✅✅
https / httpOpen web browser app, eg: https://expo.io✅✅

If you want to enable deep links in your app, please read the below guide:

For instructions on how to add support for deep linking on Android, refer to Enabling Deep Links for App Content - Add Intent Filters for Your Deep Links.

If you wish to receive the intent in an existing instance of MainActivity, you may set the launchMode of MainActivity to singleTask in AndroidManifest.xml. See <activity> documentation for more information.

<activity
  android:name=".MainActivity"
  android:launchMode="singleTask">

There are two ways to handle URLs that open your app.

1. If the app is already open, the app is foregrounded and a Linking 'url' event is fired​

You can handle these events with Linking.addEventListener('url', callback) - it calls callback({url}) with the linked URL

2. If the app is not already open, it is opened and the url is passed in as the initialURL​

You can handle these events with Linking.getInitialURL() - it returns a Promise that resolves to the URL, if there is one.

Example​

Open Custom Settings​

Send Intents (Android)​

Reference

Methods​

addEventListener()​

static addEventListener(
  type: 'url',
  handler: (event: {url: string}) => void,
): EmitterSubscription;

Add a handler to Linking changes by listening to the url event type and providing the handler.

canOpenURL()​

static canOpenURL(url: string): Promise<boolean>;

Determine whether or not an installed app can handle a given URL.

The method returns a Promise object. When it is determined whether or not the given URL can be handled, the promise is resolved and the first parameter is whether or not it can be opened.

The Promise will reject on Android if it was impossible to check if the URL can be opened or when targetting Android 11 (SDK 30) if you didn't specify the relevant intent queries in AndroidManifest.xml. Similarly on iOS, the promise will reject if you didn't add the specific scheme in the LSApplicationQueriesSchemes key inside Info.plist (see bellow).

Parameters:

NameTypeDescription
url
Required
stringThe URL to open.

For web URLs, the protocol ("http://", "https://") must be set accordingly!

This method has limitations on iOS 9+. From the official Apple documentation:

  • If your app is linked against an earlier version of iOS but is running in iOS 9.0 or later, you can call this method up to 50 times. After reaching that limit, subsequent calls always resolve to false. If the user reinstalls or upgrades the app, iOS resets the limit.

As of iOS 9, your app also needs to provide the LSApplicationQueriesSchemes key inside Info.plist or canOpenURL() will always resolve to false.

When targeting Android 11 (SDK 30) you must specify the intents for the schemes you want to handle in AndroidManifest.xml. A list of common intents can be found here.

For example to handle https schemes the following needs to be added to your manifest:

<manifest ...>
    <queries>
        <intent>
            <action android:name="android.intent.action.VIEW" />
            <data android:scheme="https"/>
        </intent>
    </queries>
</manifest>

getInitialURL()​

static getInitialURL(): Promise<string | null>;

If the app launch was triggered by an app link, it will give the link url, otherwise it will give null.

To support deep linking on Android, refer http://developer.android.com/training/app-indexing/deep-linking.html#handling-intents

getInitialURL may return null while debugging is enabled. Disable the debugger to ensure it gets passed.

openSettings()​

static openSettings(): Promise<void>;

Open the Settings app and displays the app’s custom settings, if it has any.

openURL()​

static openURL(url: string): Promise<any>;

Try to open the given url with any of the installed apps.

You can use other URLs, like a location (e.g. "geo:37.484847,-122.148386" on Android or "http://maps.apple.com/?ll=37.484847,-122.148386" on iOS), a contact, or any other URL that can be opened with the installed apps.

The method returns a Promise object. If the user confirms the open dialog or the url automatically opens, the promise is resolved. If the user cancels the open dialog or there are no registered applications for the url, the promise is rejected.

Parameters:

NameTypeDescription
url
Required
stringThe URL to open.

This method will fail if the system doesn't know how to open the specified URL. If you're passing in a non-http(s) URL, it's best to check canOpenURL() first.

For web URLs, the protocol ("http://", "https://") must be set accordingly!

This method may behave differently in a simulator e.g. "tel:" links are not able to be handled in the iOS simulator as there's no access to the dialer app.

sendIntent()
Android
​

static sendIntent(
  action: string,
  extras?: Array<{key: string; value: string | number | boolean}>,
): Promise<void>;

Launch an Android intent with extras.

Parameters:

NameType
action
Required
string
extrasarray of {key: string, value: string \| number \| boolean}