Mobile App Event Schema: The Complete Reference

Mobile apps don’t behave like websites. Sessions are shorter, users switch between foreground and background constantly, and half the events you care about — push notifications, permission prompts, app updates — don’t exist on the web at all. If you paste your website event schema into a mobile app, you’ll miss what actually matters.

This reference covers every mobile and app event you should track in GA4 and Firebase: from install and onboarding through core engagement, monetization, and retention loops. Each event includes its trigger, key parameters, and a ready-to-use data layer snippet. I’ve implemented this schema across eight mobile apps — three iOS-only, three Android-only, and two cross-platform with Flutter — and the patterns hold regardless of platform or framework.

Install and Onboarding Events

The first 60 seconds after install determine whether a user sticks around. Onboarding completion is the single strongest predictor of Day 7 retention in every app I’ve worked on. Track every step — not just the finish line.

// Install and onboarding — data layer push
dataLayer.push({
  event: "onboarding_step_completed",
  step_number: 3,
  step_name: "enable_notifications",
  time_on_step: 8.4
});

Why it matters: Onboarding drop-off analysis tells you exactly where users give up. In one fitness app I instrumented, 38% of users abandoned at the “enable notifications” step. We moved that permission request to after the first workout — completion rate jumped from 62% to 81%, and Day 7 retention improved by 15 percentage points.

Session and Lifecycle Events

Mobile sessions are fundamentally different from web sessions. Users open an app dozens of times per day for seconds at a time. Firebase handles session_start automatically, but you need additional events to understand the app lifecycle — foreground, background, updates, and crashes.

// Session lifecycle — data layer push
dataLayer.push({
  event: "app_opened",
  open_type: "deep_link",
  time_in_background: 3420,
  deep_link_url: "myapp://product/shoes-42"
});

Why it matters: The open_type parameter on app_opened reveals how users return to your app — cold start, warm resume, push notification, or deep link. This single parameter tells you which re-engagement channels actually work. In a food delivery app, we found that deep links from email drove 2.3× more orders per session than push notifications, which led to a complete reallocation of the retention budget.

Permission and System Events

Mobile apps depend on system permissions — notifications, location, camera, contacts. Each permission prompt is a conversion event. If a user denies notifications, your entire push-based retention strategy breaks. Track every prompt and every response.

// Permission tracking — data layer push
dataLayer.push({
  event: "permission_granted",
  permission_type: "push_notifications",
  prompt_context: "after_first_order",
  grant_count: 1
});

Why it matters: iOS gives you one shot at the system notification prompt — if the user denies it, you can’t ask again without sending them to Settings. The prompt_context parameter lets you A/B test when to show the prompt. I’ve seen notification opt-in rates range from 35% (shown during onboarding) to 72% (shown after the user completes a valuable action). That difference can double your push-driven retention.

Core Engagement Events

These are the actions that define your app’s core loop — the reason users come back. They vary by app category, but the tracking pattern is the same: capture what happened, how long it took, and what the outcome was.

// Core engagement — data layer push
dataLayer.push({
  event: "action_completed",
  action_type: "workout_finished",
  duration: 1845,
  result: "completed",
  is_first_time: false
});

Why it matters: The action_completed event with is_first_time parameter is your activation signal. Track the first time a user completes your app’s core action — first workout, first order, first message sent. This “aha moment” is what separates users who retain from those who churn. In a language learning app, users who completed their first lesson within 2 hours of install had 4× the 30-day retention rate.

Monetization Events

Mobile monetization models differ from web — in-app purchases, subscriptions, ad revenue, and freemium conversions all need dedicated tracking. Firebase handles some in_app_purchase events automatically, but you need subscription lifecycle events for real revenue analytics.

// Monetization — data layer push
dataLayer.push({
  event: "subscription_started",
  plan_id: "pro_yearly",
  price: 59.99,
  currency: "EUR",
  billing_period: "annual",
  is_trial_conversion: true
});

Why it matters: The is_trial_conversion flag on subscription_started is critical for understanding your funnel. Trial-to-paid conversion rates vary dramatically — I’ve seen 15% for generic free trials but 45% for trials that require a payment method upfront. Track paywall_viewed with trigger_context to understand which feature gates drive the most conversions.

Retention and Re-engagement Events

Mobile retention is measured in days — Day 1, Day 7, Day 30. These events track the mechanisms that bring users back: push notifications, streaks, reminders, and the moments users decide to leave.

// Retention — data layer push
dataLayer.push({
  event: "streak_updated",
  streak_count: 14,
  streak_type: "daily_login",
  is_new_record: true
});

Why it matters: Streaks are one of the most powerful retention mechanics in mobile. The streak_broken event with recovery_offered parameter lets you measure whether streak recovery features (like “freeze” tokens) actually save users. In a meditation app, offering streak recovery at the moment of breakage retained 40% of users who would have otherwise dropped off permanently.

Mobile-Specific Metrics and KPIs

These events feed the metrics that mobile product teams report on weekly. Here’s how they connect.

Implementation Checklist

Further Reading

• Firebase Analytics Events — automatically collected and recommended events
• GA4 App Stream Setup — connecting your app to Google Analytics
• Apple App Store Subscriptions — server-side subscription event handling
• Google Play Billing — subscription and in-app purchase integration