RevenueCat provides a source of truth for a subscriber's status across different platforms. To do this, each subscriber has an App User ID that uniquely identifies them within your application.

User identity is one of the most important components of many mobile applications, and it's extra important to make sure the subscription status RevenueCat is tracking gets associated with the correct user.

The Purchases SDK allows you to specify your own user identifiers or use anonymous identifiers generated by RevenueCat. Some apps will use a combination of their own identifiers and RevenueCat anonymous IDs - that's okay!

Anonymous App User IDs

If you don't provide an App User ID when instantiating the Purchases SDK, RevenueCat will generate a new random App User ID for you and cache it on the device. In the event that the user deletes and reinstalls the app, a new random App User ID will be generated.

Purchases.configure(withAPIKey: "my_api_key")

[RCPurchases configureWithAPIKey:@"my_api_key"];

Purchases.configure(PurchasesConfiguration.Builder(this, "api_key").build())

Purchases.configure(new PurchasesConfiguration.Builder(context, "api_key").build());

await Purchases.setup("public_sdk_key");

Purchases.setup("public_sdk_key");

Purchases.setup("public_sdk_key");

See Unity installation instructions https://docs.revenuecat.com/docs/unity

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Anonymous App User IDs are always prefixed with $RCAnonymousID: for SDK versions 3+. This can be useful for working with anonymous users on your server.

Logging In with a Custom App User ID

Setting your own App User ID will allow you to reference users in the RevenueCat dashboard, via the API, as well as in the webhooks and other integrations.

Using an externally managed App User ID also provides a mechanism by which to restore purchases in a few scenarios:

• When a user deletes and reinstalls your app - using the same App User ID will ensure they still have access to subscriptions previously started without requiring a restore .
• When the user logs in on multiple devices - you can honor a subscription that was purchased on one device across any other platform.

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App User IDs are case-sensitive.

Provide App User ID on configuration

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iOS 15+ Prewarming

In certain cases, iOS may prewarm your app - this essentially means your app will be launched silently in the background to improve app launch times for your users.

If you are not using RevenueCat's anonymous IDs as described above, and are instead providing your own app user ID on configuration, do not call configure in application:didFinishLaunchingWithOptions:. Instead, call the configure method in your root view controller's initialization method.

If you have your own App User IDs at app launch, you can pass those on instantiation to Purchases.

Purchases.configure(withAPIKey: "my_api_key", appUserID: "my_app_user_id")

[RCPurchases configureWithAPIKey:@"my_api_key" appUserID:@"my_app_user_id"];

Purchases.configure(PurchasesConfiguration.Builder(this, "api_key").appUserID("my_app_user_id").build())

Purchases.configure(new PurchasesConfiguration.Builder(context, "api_key").appUserID("my_app_user_id").build());

await Purchases.setup("public_sdk_key", appUserId: "my_app_user_id");

Purchases.setup("public_sdk_key", "my_app_user_id");

Purchases.setup("public_sdk_key", "my_app_user_id");

See Unity installation instructions https://docs.revenuecat.com/docs/unity

Often times, you may not have your own App User IDs until later in the application lifecycle. In these cases, you can pass the App User ID later through the .logIn() method.

Provide App User ID after configuration

If your app doesn't receive its own App User ID until later in its lifecycle, you can set (or change) the App User ID at any time by calling .logIn(). If the logged in identity does not already exist in RevenueCat, it will be created automatically.

// Configure Purchases on app launch
Purchases.configure(withAPIKey: "my_api_key")

//...

// Later log in provided user Id
Purchases.shared.logIn("my_app_user_id") { (customerInfo, created, error) in
    // customerInfo updated for my_app_user_id
}

// Configure Purchases on app launch
[RCPurchases configureWithAPIKey:@"my_api_key"];

//...

// Later log in provided user Id
[[RCPurchases sharedPurchases] logIn:@"my_app_user_id" completionBlock:^(RCPurchaserInfo *purchaserInfo, Bool *created, NSError *error) {
    // purchaserInfo updated for my_app_user_id
}];

// Configure Purchases on app launch
Purchases.configure(PurchasesConfiguration.Builder(this, "api_key").build())
  
//...

// Later log in provided user Id
Purchases.sharedInstance.loginWith("my_app_user_id", ::showError) { customerInfo, created ->
  // customerInfo updated for my_app_user_id
}

// Configure Purchases on app launch
Purchases.configure(new PurchasesConfiguration.Builder(context, "api_key").build());

//...

// Later log in provided user Id
Purchases.getSharedInstance().logIn("my_app_user_id", new LogInCallback() {
    @Override
    public void onReceived(@NotNull CustomerInfo customerInfo, boolean created) {
        // customerInfo updated for my_app_user_id
    }
  
  @Override
  public void onError(@NotNull PurchasesError error) {

  }
});

// Configure Purchases on app launch
await Purchases.setup("public_sdk_key");

//...

// Later log in provided user Id
LogInResult result = await Purchases.logIn("my_app_user_id");

// Configure Purchases on app launch
Purchases.setup("public_sdk_key");

//...

// Later log in provided user Id
const { purchaserInfo, created } = await Purchases.logIn("my_app_user_id");
// purchaserInfo updated for my_app_user_id

// Configure Purchases on app launch
Purchases.setup("public_sdk_key");

//...

// Later log in provided user Id

Purchases.logIn(
  "my_app_user_id", 
  ({ purchaserInfo, created }) => {
    // purchaserInfo updated for my_app_user_id
  },
  error => {
  }
);

purchases.LogIn("my_app_user_id", (purchaserInfo, created, error) => {
  // purchaserInfo updated for my_app_user_id
});

logIn() method alias behavior

When going from an Anonymous ID to a custom App User ID RevenueCat will decide whether the identities should be merged (aliased) into the same CustomerInfoCustomerInfo - Also known as PurchaserInfo. Contains all of the purchase and subscription data available about the user. object or not depending on the state of the custom App User ID and if it already has an anonymous alias.

Logging Out

When an identified user logs out you should call the logOut() method - this generates a new Anonymous App User ID for the logged out state.

Logging back in

To log in a new user, the provided App User ID should be set again with .logIn().

Switching accounts

If you need to switch from one provided App User ID to another, it's okay to call the .logIn() method directly - you do not need to call logOut() first.

Sharing Subscriptions Across Apps and Platforms

Apps within the same RevenueCat Project share the same App User ID namespace, which means that they also share subscriptions. A user logged in to the same user ID in different apps of the same Project will have access to the same entitlements. This allows sharing of subscription status between different apps, even on different platforms.

Note that anonymous App User IDs are not able to share subscription status across apps and platforms, so you'll need to identify with a custom App User ID via your own authentication system.

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Managing Subscriptions

A user can only manage their subscription on the platform it was purchased from.

Tips for Setting App User IDs

Next Steps

• Enrich your app by reacting to the user's current subscription status
• If you're moving to RevenueCat from another system, see our guide on migrating your existing subscriptions
• Once you're ready to test your integration, you can follow our guides on testing and debugging