The app asks for permission
iOS always shows a prompt; Android 13 and later need the POST_NOTIFICATIONS runtime permission.
APNs vs FCM: Push Notifications for iOS and Android Compared
APNs is Apple's service for delivering push notifications to iPhone, iPad, Mac and Apple Watch; FCM is Google's free service for Android, which can also send to iOS (through APNs) and web browsers. Every push to an Apple device ultimately goes through APNs, so the real choice is whether your backend talks to APNs directly for iOS or sends everything through FCM. Both cap payloads at 4 KB, both are free, and both deliver on a best-effort basis, so reliable notifications depend on token management, the right priority and time-to-live, and an app that refreshes state when opened. For most apps, we recommend FCM as one API for Android, iOS and web, with direct APNs only when you need iOS-specific features such as Live Activities or VoIP at scale.
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- APNs is required for all Apple devices; FCM covers Android and can wrap APNs for iOS and add web push.
- Both are free and cap the payload at 4 KB, so send an ID and fetch details from your API.
- Use FCM's HTTP v1 API; the legacy FCM APIs were shut down in 2024.
- Treat tokens as changing addresses: update them on every app start and remove them on "unregistered" errors.
- Huawei phones without Google services need Huawei Push Kit; plan for it if you have users in China or on newer Huawei devices.
APNs vs FCM at a Glance
A quick comparison of APNs and FCM, highlighting their key features, platform compatibility, and differences in push notification delivery.
| Comparison | APNs (Apple Push Notification service) | FCM (Firebase Cloud Messaging) |
|---|---|---|
| Owner | Apple | |
| Devices | iPhone, iPad, Mac, Apple Watch, Apple TV, Vision Pro, Safari web push | Android, iOS (via APNs), web browsers |
| Cost | Free with an Apple Developer account | Free |
| Server API | HTTP/2 provider API | HTTP v1 API (legacy APIs shut down in 2024) |
| Authentication | Token-based (.p8 key, signed JWT) or TLS certificate | OAuth 2.0 access token from a Google service account |
| Max payload | 4 KB (5 KB for VoIP) | 4 KB |
| Priority | 10 (immediate), 5 (power-aware), 1 (lowest) | High or normal |
| Expiry | apns-expiration timestamp | TTL up to 4 weeks |
| Replace older messages | apns-collapse-id (up to 64 bytes) | collapse_key (up to 4 active keys per device on Android) |
| Group sends | No topics; send per device or use broadcast for Live Activities | Topics and conditions, device groups |
| Silent/background push | content-available, throttled by iOS | Data-only messages, limited by Android background rules |
| Rich media | Notification Service Extension with mutable-content | Image field, expanded layouts on Android |
| Analytics | Delivery status via Push Notifications Console | Delivery data and reports in Firebase console and BigQuery export |
How Push Notifications Reach a Phone
Understand how push notifications travel from your server through APNs or FCM to a user’s device, enabling timely alerts, real-time updates, and better app engagement across platforms.
This process involves device tokens, notification payloads, and platform-specific services to ensure messages reach users efficiently, even when the app is running in the background.
The app gets a token
iOS returns an APNs device token; Android (and iOS when using the Firebase SDK) returns an FCM registration token.
The app sends the token to your backend,
along with the user ID, platform, app version and environment.
Your backend sends a message
to APNs or FCM with the token, the payload and delivery options such as priority and expiry.
APNs or FCM delivers it
over a persistent connection the operating system keeps open, so your app does not need to be running.
The device shows it or hands it to the app,
depending on the message type, the app state and the user's notification settings.
Setting Up APNs
Authentication
Create an APNs authentication key (.p8) in your Apple Developer account and sign a JSON Web Token with it for each connection. One key works for all your apps and never expires; the older certificate method needs yearly renewal per app.
Endpoints and Environments
Send to the development (sandbox) endpoint for debug builds and the production endpoint for TestFlight and App Store builds. Tokens from one environment do not work in the other.
Required Headers
apns-topic (your bundle ID), apns-push-type (alert, background, voip, liveactivity and others), and optionally apns-priority, apns-expiration and apns-collapse-id.
Payload
A JSON aps dictionary with alert (title, subtitle, body), badge, sound, thread-id, interruption-level and relevance-score, plus your own keys.
Setting Up FCM
Firebase Project
Add your Android and iOS apps to a Firebase project and include the Firebase Messaging SDK.
Authentication
Your server uses a Google service account to get short-lived OAuth 2.0 access tokens for the HTTP v1 API, usually through the Firebase Admin SDK.
iOS Through FCM
Upload your APNs .p8 key to the Firebase project; FCM then forwards iOS messages to APNs for you.
Message Types
Notification messages (shown by the system when the app is in the background), data messages (handled by your app code), or both, with platform-specific android, apns and webpush blocks for fine control.
Payload and Message Structure Compared
Explore how APNs and FCM structure notification payloads, handle message data, and support custom content to deliver relevant alerts and personalized user experiences across mobile platforms.
| Comparison | APNs | FCM |
|---|---|---|
| Maximum size | 4,096 bytes (5,120 for VoIP) | 4,096 bytes |
| Display fields | aps.alert: title, subtitle, body | notification: title, body, image |
| Custom data | Any extra JSON keys outside aps | data: string key-value pairs only |
| Badge | aps.badge (number) | Android: notification count; iOS via apns block |
| Grouping | thread-id | tag (Android), thread-id via apns block |
| Interruption level | passive, active, time-sensitive, critical | Android notification channel importance |
Delivery Controls Compared
Compare how APNs and FCM manage notification delivery, including priority settings, message expiration, delivery timing, and platform-specific controls that help developers send alerts reliably.
| Control | APNs | FCM |
|---|---|---|
| Priority | 10 = deliver now and wake the device; 5 = deliver when power-efficient; 1 = lowest | high = deliver now, may wake the device; normal = may wait for the device to wake |
| Expiry | apns-expiration (0 = try once, then discard) | ttl, from 0 seconds up to 4 weeks (default 4 weeks) |
| Replace older messages | apns-collapse-id: newer message replaces the older one | collapse_key: up to 4 different keys held per Android device |
| Offline storage | Keeps only the latest notification per app when the device is offline | Stores messages until TTL expires (subject to limits) |
| Throttling | Background pushes limited by iOS; too many high-priority pushes get throttled | High-priority messages that don't show a notification can be downgraded to normal |
Silent, Background and Special Push Types
Silent (Background) Pushes
APNs content-available pushes and FCM data-only messages wake your app to refresh content. Both operating systems limit them to protect battery: Apple recommends no more than a few per hour, and Android may delay them under Doze and battery optimisation.
Rich Notifications
On iOS, set mutable-content and use a Notification Service Extension to download images, decrypt content or change the text before it shows. On Android, FCM's image field and custom layouts give expanded notifications.
Actionable Notifications
iOS notification categories and Android notification actions let users reply, approve, track or snooze without opening the app.
Live Activities and Widgets
Live Activities on the lock screen and Dynamic Island are updated by APNs liveactivity pushes, including broadcast updates to many users at once; FCM can send these through its apns block.
VoIP and Calls
iOS VoIP pushes through PushKit must report an incoming call with CallKit immediately. Android uses high-priority FCM data messages with a full-screen intent.
Web Push
FCM supports web push for Chrome, Firefox and Edge. Safari, including web apps added to the iPhone home screen from iOS 16.4, uses the standard Web Push protocol.
Why Notifications Go Missing
Stale tokens
tokens change after reinstalls, restores and refreshes; APNs returns 410 Unregistered and FCM returns UNREGISTERED for dead ones.
Wrong environment or credentials
sandbox tokens sent to production APNs, an expired certificate, or the wrong Firebase project.
Payload over 4 KB
or invalid JSON.
Permissions and settings
notifications denied, Focus or Do Not Disturb, disabled Android channels, battery savers.
Silent push throttling
background pushes delayed or dropped by the OS.
App handling
messages received in the foreground but never displayed by the app.
Devices without Google services
many newer Huawei phones cannot receive FCM and need Huawei Push Kit.
Troubleshooting Checklist
Identify and resolve common push notification issues with a practical checklist covering device tokens, permissions, payload formatting, authentication, and delivery errors across APNs and FCM.
Use these troubleshooting steps to diagnose failed notifications, verify server configurations, and improve reliable message delivery on iOS and Android devices.
Confirm the token
your server used is the latest one the app reported for that user and device.
Check the provider response
and store the error code with every send.
Send a minimal test
(title and body only) to separate transport problems from payload problems.
Verify environment and credentials
APNs key, team ID, bundle ID and endpoint; FCM project and service account.
Check device settings
permission, Focus mode, Android channel importance, battery restrictions.
Check app handling
in foreground, background and killed states.
Use the tools
Apple's Push Notifications Console and Firebase's message delivery reports show where a message stopped.
Which Setup Should You Use?
Choose the right push notification setup based on your target platforms, app architecture, delivery requirements, and development resources to ensure reliable communication across iOS and Android devices.
| Your situation | Recommended setup | Why |
|---|---|---|
| Android and iOS app, standard notifications | FCM for both platforms | One API, one token type, topics and analytics in one place |
| iOS-only app | APNs directly | No extra dependency; full access to every APNs feature |
| Heavy use of Live Activities, VoIP or time-sensitive iOS alerts | APNs directly for iOS, FCM for Android | Full control of APNs headers and push types |
| Users on Huawei devices without Google services | Add Huawei Push Kit alongside FCM | FCM cannot reach these devices |
| Marketing campaigns, segmentation, A/B tests | A messaging platform (OneSignal, Braze, Airship, CleverTap, MoEngage) on top of APNs and FCM | Segments, journeys and analytics without building them |
| Very high volume or strict data control | Your own notification service talking to APNs and FCM | Control of queues, retries, logging and data residency |
What Push Notifications Cost
Need push built into your app? See our iOS app development services, Android app development services and Firebase iOS app development.
APNs and FCM
free to use; APNs only needs your Apple Developer Program membership.
Messaging platforms
free tiers for small apps, then monthly fees that grow with users and channels.
Building it into your app
basic push for one app typically takes 1–2 weeks of development ($2,000–$6,000); a custom notification service with preferences, scheduling, segments, rich media, Live Activities and analytics costs $10,000–$40,000.
Best Practices for Reliable Push
Manage Tokens Carefully
Send the token on every app start, store it with user, platform, environment and last-seen time, update it on refresh, remap it on logout, and delete it on unregistered errors.
Keep Payloads Small
Stay well under 4 KB; send IDs, not full records, and let the app fetch details.
Choose Priority and Expiry on Purpose
High priority only for messages the user must see now; short expiry for time-sensitive alerts such as OTPs and ride updates.
Ask for Permission at the Right Moment
Explain the value first (order updates, price alerts) and ask after a related action, not on first launch.
Let Users Choose
Notification preferences by type, quiet hours, Android channels and iOS interruption levels reduce opt-outs.
Don't Rely on Push for Critical State
Delivery is best-effort; important information must also be in the app and, where needed, by SMS or email.
Measure Everything
Log sends, provider responses, deliveries, opens and opt-outs to find problems and improve engagement.
Protect Privacy
Avoid sensitive data in visible notification text; encrypt content and decrypt it in a Notification Service Extension when needed.
Need Reliable Push Notifications in Your App?
Our iOS, Android and backend engineers set up APNs and FCM, token management, rich and silent notifications, Live Activities and delivery analytics, and fix pushes that go missing. Tell us about your app and we'll send a recommended setup, timeline and cost within 2 business days.
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Frequently Asked Questions
What is the difference between APNs and FCM?
APNs is Apple's service and the only way to deliver remote notifications to iPhones, iPads, Macs and Apple Watches. FCM is Google's service that delivers to Android directly and to iOS by forwarding messages through APNs, giving you one API for both platforms.
Does FCM work on iOS?
Yes. FCM sends iOS notifications through APNs, so you still need an Apple Developer account and an APNs authentication key uploaded to your Firebase project.
Should I use FCM or APNs for my iOS app?
Use FCM if you also have an Android app and want one backend integration. Use APNs directly for iOS-only apps or when you need full control of Apple features such as Live Activities, VoIP pushes and time-sensitive interruption levels.
Are APNs and FCM free?
Yes. Both are free to use. APNs requires an Apple Developer Program membership ($99 a year), and FCM has no per-message charge.
What is the maximum payload size for APNs and FCM?
4 KB for standard notifications on both. APNs allows 5 KB for VoIP notifications.
Should I use a .p8 key or a .p12 certificate for APNs?
Use a .p8 token-based authentication key. It does not expire each year, works for all your apps in the team and both sandbox and production environments.
Why are my iOS push notifications not arriving?
The most common causes are a sandbox and production environment mismatch, a missing or wrong APNs key in Firebase, a stale device token, notifications disabled by the user, Focus mode, or a background (silent) push being throttled by iOS.
What is the difference between notification and data messages in FCM?
Notification messages are displayed by the system automatically when the app is in the background. Data messages are handled by your app's code, which gives you control over how and whether they are shown.
Are silent push notifications guaranteed to be delivered?
No. iOS and Android limit background pushes to save battery, so silent pushes can be delayed or dropped. Use them to refresh content, not for anything critical.
How often do push tokens change?
Tokens can change when the app is reinstalled, restored to a new device or data is cleared. Send the latest token to your server on every app start and remove tokens that return unregistered errors.
Do I need Huawei Push Kit?
Only if you have users on Huawei devices without Google Play services, because FCM cannot deliver to them.
Can I send web push notifications with APNs and FCM?
Yes. FCM supports web push in browsers, and Safari on macOS and iOS 16.4+ (for web apps added to the home screen) supports standard Web Push.