You paid for an app so you could reach your customers directly. Then you learn that half of them never said yes to notifications, and your "50% off" message went to almost nobody. Or worse, people who did get it uninstalled the app.
Push notifications are the short messages an app shows on the phone's lock screen or top bar, even when the app is closed. This guide explains how they reach the phone, what they cost, the permission rules on Android and iPhone, and how to use them without annoying the people who pay you.
Quick answer
How push notifications work, step by step
Your app's server writes the message and sends it to a delivery service run by Google or Apple. That service finds the right phone and shows the message. The phone does not need your app open for this to happen.
The path looks like this:
- When a customer installs your app, the phone gets a unique address called a token (a long code that points to that phone and that app).
- Your app sends this token to your server, so the server knows where to reach this customer.
- When there is news, such as "Your order is out for delivery", your server sends the message and the token to the delivery service.
- The delivery service passes the message to the phone, and the phone shows it.
Who carries the message?
For Android phones, the usual carrier is Google's Firebase Cloud Messaging, called FCM. Google's documentation calls it "a cross-platform messaging solution that lets you reliably send messages". It works for Android, iPhone and websites.
For iPhones, every message goes through Apple's own service, the Apple Push Notification service (APNs). Firebase's iPhone setup guide asks developers to upload an APNs key from the Apple Developer account into Firebase. So one Firebase setup can reach both kinds of phone.
How much can one message carry?
Firebase's docs say a message can carry up to 4,096 bytes of data. That is enough for a short title, a line of text and a link to the right screen in your app. It is not meant for long content.
Firebase push notification cost: is it really free?
Yes, the message delivery itself is free. Firebase's pricing page lists Cloud Messaging as "No-cost" on both the Spark (free) plan and the Blaze (pay as you go) plan, as of October 2026. The costs you do pay are around it.
| Cost item | Who charges | What it depends on |
| Sending messages through FCM | Google Firebase | No cost, as of October 2026 |
| The server that decides when to send | Your hosting or cloud provider | How many customers and how often you send |
| Apple developer membership (needed for the APNs key) | Apple | US$99 a year, as of October 2026 |
| Building the screens, rules and settings in the app | Your developer | How many message types and settings you want |
Other push notification services also exist, some of them paid. Before you sign up for one, ask your developer what it adds over FCM and APNs, and check its price page.
What changed with the Android 13 permission?
Since Android 13, notifications are switched off by default for newly installed apps. The app must ask, and the customer must tap Allow, before any normal notification appears. Android's developer guide calls this the POST_NOTIFICATIONS permission (the phone's yes or no switch for your app's notifications).
When should the app ask?
Google's guide says to let people get to know your app first. Its examples of good moments include after the user "submits an order for food delivery" or after the third or fourth time they open the app. Asking on the very first screen, before the customer knows why, wastes your one good chance.
There is a catch for older apps. If an app is still built for Android 12L or lower, Android shows the request at its own time, usually at startup. If the customer taps "Don't allow" there, they will not be asked again until they reinstall, or until the app is updated for Android 13.
What about iPhone?
Apple's developer documentation says "you must obtain permission" before showing alerts, sounds or badges. It suggests asking in context, for example after a person schedules their first task in a reminder app. Apple also offers a quiet trial mode, where messages appear only in Notification Center, so people can decide after seeing a few.
| Phone | Is permission needed? | When to ask |
| Android 13 and newer | Yes, off by default for new installs | At a useful moment, such as after the first order |
| Android 12L and older phones | No separate prompt, the permission arrived in Android 13 | Not applicable |
| iPhone | Yes, for alerts, sounds and badges | In context, or start with Apple's quiet trial mode |
The rules against spam
Both stores have rules, and breaking them can cost you your app's sending rights. Your developer can build the app correctly, but you decide what gets sent.
Apple's rule for marketing messages
Apple's App Review Guidelines, rule 4.5.4, say push notifications "must not be required for the app to function". They must not carry "sensitive personal or confidential information". Promotions and direct marketing are allowed only if customers have "explicitly opted in" through consent text in your app, and can opt out inside the app.
Apple is clear about the risk. If you send offers on iPhone without that opt-in screen, Apple says abuse "may result in revocation" of your push privileges. Plan the consent screen before launch, not after the first complaint.
Let customers choose what they get
Android has notification channels, which are separate groups like "Order updates" and "Offers". Android's guide says that since Android 8.0, every notification must belong to a channel, and users decide which channels "can be intrusive or visible". If everything sits in one group, a customer who is tired of offers will switch off your order updates too.
A push notification service plan for a small business app
Most business apps need only three or four message types. Plan them on one page before the developer starts, using a list like this.
| Message type | Example | Opt-in needed? |
| Order or booking update | "Your table for 4 is confirmed for 8 pm" | Normal notification permission |
| Reminder the customer asked for | "Your appointment is tomorrow at 11 am" | Normal notification permission |
| Offer or promotion | "Diwali sweets are back this week" | Separate marketing opt-in on iPhone |
| Account or security alert | "New login on your account" | Keep details out of the message text |
If you are planning a new app and want notifications planned in from day one, read about The Beyond Horizon's mobile app development for Indian businesses.
Write messages people want to open
Apple's design guide gives simple advice. Keep messages short, do not send several messages about the same thing, and keep private details out. It warns that repeat messages fill up Notification Center and "people may turn off all notifications from your app".
Make the tap open the right screen
A message that opens only your app's home page wastes the customer's tap. Ask for each message to open the exact screen it talks about, such as the order tracker or the booking page. Developers call this a deep link (a link that opens a particular screen inside the app).
On iPhone, Apple's design guide says a notification can also show up to four buttons that let people act without opening the app. A booking reminder could offer "Confirm" and "Reschedule", for example. Keep these for simple, common actions.
A tip most first-time owners miss
Ask your developer to set up the Firebase project and the APNs key under your business's own Google and Apple accounts. If both sit in the developer's personal accounts, you cannot send messages or change settings once they leave. Ask for owner access in writing at handover.
A closing note
Push notifications are cheap to send and easy to overuse. The value comes from asking at the right moment, splitting messages into clear groups and sending only what the customer expects.
If you want help planning the notifications for your app, call or WhatsApp The Beyond Horizon on +91 75973 92744.