Notification messages vs data messages in Firebase - Hands-On Comparison

Notification messages vs data messages

📖 Scenario: You are building a mobile app that needs to send messages to users. Some messages should show a notification automatically, while others should send data silently for the app to handle.

🎯 Goal: Learn how to create Firebase Cloud Messaging payloads for notification messages and data messages, and understand their differences.

📋 What You'll Learn

Create a notification message payload with title and body

Create a data message payload with custom key-value pairs

Add a condition to select message type

Complete the final payload structure for sending

💡 Why This Matters

🌍 Real World

Mobile apps use Firebase Cloud Messaging to notify users or send data updates silently.

💼 Career

Understanding message payloads is essential for backend developers and cloud engineers working with push notifications.

1

Create a notification message payload

Create a dictionary called notification_message with keys title set to "Hello User" and body set to "You have a new alert".

Firebase

# Create notification_message dictionary with title and body
# Your code here

Hint

Use a dictionary with keys 'title' and 'body' for the notification message.

2

Create a data message payload

Create a dictionary called data_message with keys action set to "update" and item_id set to "12345".

Firebase

notification_message = {
    "title": "Hello User",
    "body": "You have a new alert"
}
# Create data_message dictionary with action and item_id
# Your code here

Hint

Use a dictionary with keys 'action' and 'item_id' for the data message.

3

Add a message type selector

Create a variable called use_notification and set it to True. Then create a variable called message_payload that is notification_message if use_notification is True, otherwise data_message.

Firebase

notification_message = {
    "title": "Hello User",
    "body": "You have a new alert"
}
data_message = {
    "action": "update",
    "item_id": "12345"
}
# Create use_notification variable and message_payload selection
# Your code here

Hint

Use a boolean variable and a conditional expression to select the payload.

4

Complete the final Firebase message payload

Create a dictionary called firebase_message with a key message whose value is a dictionary containing token set to "user_device_token" and either notification set to message_payload if use_notification is True, or data set to message_payload if use_notification is False.

Firebase

notification_message = {
    "title": "Hello User",
    "body": "You have a new alert"
}
data_message = {
    "action": "update",
    "item_id": "12345"
}
use_notification = True
message_payload = notification_message if use_notification else data_message
# Create firebase_message dictionary with message key and token, notification or data
# Your code here

Hint

Use dictionary unpacking or conditional keys to add notification or data inside the message.

Practice

1. What is the main difference between notification messages and data messages in Firebase Cloud Messaging?

easy

A. Notification messages send silent info, data messages automatically show alerts.

B. Both types always show alerts to users.

C. Notification messages automatically show alerts, data messages send silent info.

D. Data messages cannot send any information.

Solution

1. Step 1: Understand notification messages

   Notification messages are designed to automatically display alerts or notifications to the user without extra coding.

2. Step 2: Understand data messages

   Data messages send information silently to the app, which then decides how to handle or display it.

3. Final Answer:

   Notification messages automatically show alerts, data messages send silent info. -> Option C

4. Quick Check:

   Notification = alert, Data = silent info [OK]

Hint: Notification = alert shown; data = silent info sent [OK]

Common Mistakes:

• Confusing which message type shows alerts automatically
• Thinking data messages always show notifications
• Believing notification messages send silent data only

2. Which of the following is the correct JSON structure for sending a notification message with Firebase Cloud Messaging?

easy

A. { "message": { "alert": "Hello World" } }

B. { "data": { "title": "Hello", "body": "World" } }

C. { "notify": { "title": "Hello", "body": "World" } }

D. { "notification": { "title": "Hello", "body": "World" } }

Solution

1. Step 1: Identify notification message format

   Notification messages use the "notification" key with "title" and "body" fields to show alerts.

2. Step 2: Check other options for correctness

   { "data": { "title": "Hello", "body": "World" } } uses "data" which is for data messages, not notification messages. Options A and D use invalid keys.

3. Final Answer:

   { "notification": { "title": "Hello", "body": "World" } } -> Option D

4. Quick Check:

   Notification key with title/body = correct [OK]

Hint: Notification messages use "notification" key with title and body [OK]

Common Mistakes:

• Using "data" key instead of "notification" for alerts
• Using incorrect keys like "message" or "notify"
• Missing required title or body fields

3. Given this Firebase message payload sent to an Android app:

{
  "notification": { "title": "Sale", "body": "50% off!" },
  "data": { "productId": "12345" }
}

What will happen when the app receives this message?

medium

A. The message will cause an error and not be delivered.

B. The app shows a notification with title and body, and data is available for app logic.

C. The app shows only the data as a notification, ignoring title and body.

D. The app only receives silent data, no notification is shown.

Solution

1. Step 1: Analyze notification part

   The "notification" key causes the system to show a notification with the given title and body automatically.

2. Step 2: Analyze data part

   The "data" key sends extra info silently, which the app can use for logic like opening a product page.

3. Final Answer:

   The app shows a notification with title and body, and data is available for app logic. -> Option B

4. Quick Check:

   Notification shows alert + data sent silently [OK]

Hint: Notification key shows alert; data key sends silent info [OK]

Common Mistakes:

• Thinking data messages show notifications automatically
• Believing notification messages ignore data payload
• Assuming message causes error due to combined keys

4. You sent a data message with this payload:

{ "data": { "score": "100" } }

But the app does not receive it when in background. What is the likely cause?

medium

A. Data messages require app code to handle them; no notification shown automatically.

B. Data messages always show notifications automatically, so this is impossible.

C. You must include a "notification" key for data messages to work.

D. Firebase does not support data messages on Android.

Solution

1. Step 1: Understand data message behavior

   Data messages are silent and require the app's code to process them; if the app is in background, it may not receive them unless handled properly.

2. Step 2: Check other options

   Data messages always show notifications automatically, so this is impossible. is false because data messages do not show notifications automatically. You must include a "notification" key for data messages to work. is incorrect; notification key is not required for data messages. Firebase does not support data messages on Android. is false; Firebase supports data messages on Android.

3. Final Answer:

   Data messages require app code to handle them; no notification shown automatically. -> Option A

4. Quick Check:

   Data messages need app handling [OK]

Hint: Data messages need app code; no auto notification [OK]

Common Mistakes:

• Expecting data messages to show notifications automatically
• Adding notification key unnecessarily
• Believing Firebase lacks data message support

5. You want to send a message that both shows a notification alert and passes extra data to the app for custom handling. Which Firebase message payload is best?

hard

A. { "notification": { "title": "Update", "body": "New version available" }, "data": { "version": "2.0" } }

B. { "data": { "title": "Update", "body": "New version available", "version": "2.0" } }

C. { "notification": { "title": "Update" } }

D. { "message": { "alert": "Update", "info": "2.0" } }

Solution

1. Step 1: Identify combined message structure

   To show a notification and send extra data, the payload must include both "notification" and "data" keys.

2. Step 2: Evaluate options

   { "notification": { "title": "Update", "body": "New version available" }, "data": { "version": "2.0" } } correctly combines notification alert and data. { "data": { "title": "Update", "body": "New version available", "version": "2.0" } } sends all as data, so no automatic alert. { "notification": { "title": "Update" } } lacks data for extra info. { "message": { "alert": "Update", "info": "2.0" } } uses invalid keys.

3. Final Answer:

   { "notification": { "title": "Update", "body": "New version available" }, "data": { "version": "2.0" } } -> Option A

4. Quick Check:

   Combine notification + data keys for alert + info [OK]

Hint: Use both notification and data keys to combine alert and info [OK]

Common Mistakes:

• Sending all info as data without notification key
• Missing data key for extra info
• Using invalid keys like "message" or "alert"