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Showing content from https://firebase.google.com/docs/database/android/start below:

Connect your App to Firebase

Stay organized with collections Save and categorize content based on your preferences.

If you haven't already, add Firebase to your Android project.

1. Navigate to the Realtime Database section of the Firebase console. You'll be prompted to select an existing Firebase project. Follow the database creation workflow.

2. Select a starting mode for your Firebase Security Rules:

   Test mode

   Good for getting started with the mobile and web client libraries, but allows anyone to read and overwrite your data. After testing, make sure to review the Understand Firebase Realtime Database Rules section.

   Note: If you create a database in Test mode and make no changes to the default world-readable and world-writeable Rules within a trial period, you will be alerted by email, then your database rules will deny all requests. Note the expiration date during the Firebase console setup flow.

   To get started with the web, Apple, or Android SDK, select testmode.

   Locked mode

   Denies all reads and writes from mobile and web clients. Your authenticated application servers can still access your database.

3. Choose a location for the database.

   Depending on the location of the database, the URL for the new database will be in one of the following forms:

   • DATABASE_NAME.firebaseio.com (for databases in us-central1)

   • DATABASE_NAME.REGION.firebasedatabase.app (for databases in all other locations)

4. Click Done.

When you enable Realtime Database, it also enables the API in the Cloud API Manager.

In your

(usually

or

), add the dependency for the

library for Android. We recommend using the

to control library versioning.

dependencies {
    // Import the BoM for the Firebase platform
    implementation(platform("com.google.firebase:firebase-bom:34.1.0"))

    // Add the dependency for the Realtime Database library
    // When using the BoM, you don't specify versions in Firebase library dependencies
    implementation("com.google.firebase:firebase-database")
}

By using the Firebase Android BoM, your app will always use compatible versions of Firebase Android libraries.

(Alternative)  Add Firebase library dependencies without using the BoM

If you choose not to use the Firebase BoM, you must specify each Firebase library version in its dependency line.

Note that if you use multiple Firebase libraries in your app, we strongly recommend using the BoM to manage library versions, which ensures that all versions are compatible.

dependencies {
    // Add the dependency for the Realtime Database library
    // When NOT using the BoM, you must specify versions in Firebase library dependencies
    implementation("com.google.firebase:firebase-database:22.0.0")
}

The Realtime Database provides a declarative rules language that allows you to define how your data should be structured, how it should be indexed, and when your data can be read from and written to.

Retrieve an instance of your database using getInstance() and reference the location you want to write to.

You can find your Realtime Database URL in the Realtime Database section of the Firebase console. Depending on the location of the database, the database URL will be in one of the following forms:

• https://DATABASE_NAME.firebaseio.com (for databases in us-central1)
• https://DATABASE_NAME.REGION.firebasedatabase.app (for databases in all other locations)

// Write a message to the database
val database = Firebase.database
val myRef = database.getReference("message")

myRef.setValue("Hello, World!")

// Write a message to the database
FirebaseDatabase database = FirebaseDatabase.getInstance();
DatabaseReference myRef = database.getReference("message");

myRef.setValue("Hello, World!");

You can save a range of data types to the database this way, including Java objects. When you save an object the responses from any getters will be saved as children of this location.

To make your app data update in realtime, you should add a ValueEventListener to the reference you just created.

The onDataChange() method in this class is triggered once when the listener is attached and again every time the data changes, including the children.

// Read from the database
myRef.addValueEventListener(object : ValueEventListener {
    override fun onDataChange(dataSnapshot: DataSnapshot) {
        // This method is called once with the initial value and again
        // whenever data at this location is updated.
        val value = dataSnapshot.getValue<String>()
        Log.d(TAG, "Value is: $value")
    }

    override fun onCancelled(error: DatabaseError) {
        // Failed to read value
        Log.w(TAG, "Failed to read value.", error.toException())
    }
})

// Read from the database
myRef.addValueEventListener(new ValueEventListener() {
    @Override
    public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
        // This method is called once with the initial value and again
        // whenever data at this location is updated.
        String value = dataSnapshot.getValue(String.class);
        Log.d(TAG, "Value is: " + value);
    }

    @Override
    public void onCancelled(@NonNull DatabaseError error) {
        // Failed to read value
        Log.w(TAG, "Failed to read value.", error.toException());
    }
});

When using Firebase Realtime Database in your app along with ProGuard, you need to consider how your model objects will be serialized and deserialized after obfuscation. If you use DataSnapshot.getValue(Class) or DatabaseReference.setValue(Object) to read and write data, you will need to add rules to the proguard-rules.pro file:

    # Add this global rule
    -keepattributes Signature

    # This rule will properly ProGuard all the model classes in
    # the package com.yourcompany.models.
    # Modify this rule to fit the structure of your app.
    -keepclassmembers class com.yourcompany.models.** {
      *;
    }

To get help for questions or issues related to ProGuard, visit the Guardsquare Community forums to get assistance from an expert.

Before launching your app, we recommend walking through our launch checklist to make sure your app is ready to go!

Be sure to enable App Check to help ensure that only your apps can access your databases.

• Learn how to structure data for Realtime Database
• Scale your data across multiple database instances.
• Read and write data.
• View your database in the Firebase console.

Except as otherwise noted, the content of this page is licensed under the Creative Commons Attribution 4.0 License, and code samples are licensed under the Apache 2.0 License. For details, see the Google Developers Site Policies. Java is a registered trademark of Oracle and/or its affiliates.

Last updated 2025-08-15 UTC.

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