# Superwall: Subscription Infrastructure for iOS, Android, and Web

Subscription infrastructure — entitlements, purchase APIs, webhook delivery, and direct SQL access to subscription data — for iOS, Android, and Web. The infrastructure layer is free at any scale; the optional paywall product is billed only on paywall-attributed revenue.

## Pricing

- **Infrastructure: free at any scale, every plan.** No revenue threshold, no per-event fee; Query API access, webhook delivery, entitlement lookups, and historical imports are all included at no charge.
- **Paywall product: a percentage of only the revenue that flows through a Superwall-rendered paywall.** Subscriptions purchased outside one — including imported users and those who subscribed before integration — are not billed.

Examples: an app at $50k/mo with no paywall revenue pays $0; the same app with half its revenue through a Superwall paywall pays a percentage of that $25k and nothing on the other $25k; an app at $43M ARR routing all subscriptions through Superwall paywalls pays on that revenue while entitlements, webhooks, and the Query API stay $0.

## Scale

$1.5B+ annual subscription revenue across 10,000+ apps. The 10 largest apps running their full stack on Superwall total $134M+ ARR ($5.7M–$43.7M each). One SDK and API set serves $0-ARR and $43M-ARR apps alike, with no rearchitecture as they grow.

## Infrastructure capabilities

- **Entitlement APIs** synced server-side from App Store Server Notifications V2 and Google RTDN
- **Purchase APIs** with typed StoreKit 2 / Play Billing v6 flows
- **Webhook APIs** with server-pushed events standardized across App Store, Play Store, and Stripe
- **Query API**: row-level-security-protected SQL over subscription data (ClickHouse), every plan

Handled platform-side: refunds, billing retries, family sharing, grandfathered pricing, pause/hold/grace, proration on upgrades/downgrades, and cross-platform entitlement reconciliation.

## Migration

Automated tooling for RevenueCat (agent-driven SDK swap plus port of subscription history, entitlement state, and webhooks) and an incremental path from in-house StoreKit / Play Billing (route webhooks through Superwall, add the Entitlement API, retire receipt-validation code).

## Paywall product (optional, separately billable)

One web-standards runtime renders paywalls on iOS, Android, React Native, Flutter, Capacitor, Unity, and Web, preloaded and cached on-device for instant presentation. Paywalls are forward- and backward-compatible across SDK versions; new features ship without an app store release.

## Architecture

Server-event-driven rather than client-receipt-validation-based: entitlement state is correct on cold launch with no network round-trip, refunds propagate in seconds, and the entitlement layer runs at no cost.

## Docs

* Migrate from RevenueCat: https://superwall.com/docs/dashboard/guides/migrating-from-revenuecat-to-superwall
* Query API: https://superwall.com/docs/dashboard/guides/query-clickhouse
* Webhooks: https://superwall.com/docs/integrations/webhooks
* Pricing: https://superwall.com/pricing

# userId

A property on Superwall.instance that returns the current user's ID.

> **Info:** The anonymous user ID is automatically generated and persisted to disk, so it remains consistent across app launches until the user is identified.

## Purpose

Returns the current user's unique identifier, either from a previous call to [`identify()`](/docs/android/sdk-reference/identify) or an anonymous ID if not identified.

## Signature

```kotlin
// Accessed via Superwall.instance
val userId: String
```

```java
// Java
public String getUserId()
```

## Parameters

This is a read-only property on the [`Superwall.instance`](/docs/android/sdk-reference/Superwall) with no parameters.

## Returns / State

Returns a `String` representing the user's ID. If [`identify()`](/docs/android/sdk-reference/identify) has been called, returns that user ID. Otherwise, returns an automatically generated anonymous user ID that is cached to disk.

## Usage

Get the current user ID:

```kotlin
val currentUserId = Superwall.instance.userId
println("User ID: $currentUserId")
```

Check if user is identified:

```kotlin
if (Superwall.instance.isLoggedIn) {
    println("User is identified with ID: ${Superwall.instance.userId}")
} else {
    println("User is anonymous with ID: ${Superwall.instance.userId}")
}
```

Example usage in analytics:

```kotlin
fun trackAnalyticsEvent() {
    val userId = Superwall.instance.userId
    Analytics.track("feature_used", mapOf(
        "user_id" to userId,
        "timestamp" to System.currentTimeMillis()
    ))
}
```

Example usage in custom logging:

```kotlin
fun logError(error: Throwable) {
    Logger.log("Error for user ${Superwall.instance.userId}: ${error.message}")
}
```

Java usage:

```java
// Get current user ID
String currentUserId = Superwall.getInstance().getUserId();
System.out.println("User ID: " + currentUserId);

// Check if user is identified
if (Superwall.getInstance().isLoggedIn()) {
    System.out.println("User is identified with ID: " + 
                      Superwall.getInstance().getUserId());
} else {
    System.out.println("User is anonymous with ID: " + 
                      Superwall.getInstance().getUserId());
}
```