The Firebase Realtime Database is a cloud-hosted database. Data is stored asJSON and synchronized in realtime to every connected client. When you buildcross-platform apps with our Android, Apple platforms, and JavaScript SDKs, all of yourclients share one Realtime Database instance and automatically receiveupdates with the newest data.

Prerequisites

If you haven't already,install the Firebase JS SDK and initialize Firebase.

Create a Database

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

2. Select a starting mode for yourFirebase 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,makesure to review theUnderstand Firebase Realtime Database Rulessection.

   Note: If you create a database in Test mode and make no changes to thedefault world-readable and world-writeableSecurity Rules within a trialperiod, you will be alerted by email, then your database rules willdeny all requests. Note the expiration date during theFirebase consolesetup 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 thelocation of the database, theURL for the new database will be in one of the following forms:

   • DATABASE_NAME.firebaseio.com (fordatabases inus-central1)

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

4. ClickDone.

When you enableRealtime Database, it also enables the API in theCloud API Manager.

ConfigureRealtime Database Security Rules

TheRealtime Database provides a declarative rules language that allows you todefine how your data should be structured, how it should be indexed, and whenyour data can be read from and written to.

Add theRealtime Database JS SDK and initializeRealtime Database

You must specify yourRealtime Database URL when initializing the JavaScript SDK.

You can find yourRealtime Database URL in theRealtime Database section of theFirebase console. Depending on thelocation of the database, the database URL will be in one of the following forms:

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

Initialize the SDK using the following code snippet:

import{initializeApp}from"firebase/app";import{getDatabase}from"firebase/database";//TODO:Replacethefollowingwithyourapp's Firebase project configuration//See:https://firebase.google.com/docs/web/learn-more#config-objectconstfirebaseConfig={//...//Thevalueof`databaseURL`dependsonthelocationofthedatabasedatabaseURL:"https://DATABASE_NAME.firebaseio.com",};//InitializeFirebaseconstapp=initializeApp(firebaseConfig);//InitializeRealtimeDatabaseandgetareferencetotheserviceconstdatabase=getDatabase(app);

importfirebasefrom"firebase/app";import"firebase/compat/database";//TODO:Replacethefollowingwithyourapp's Firebase project configuration//See:https://firebase.google.com/docs/web/learn-more#config-objectconstfirebaseConfig={//...//Thevalueof`databaseURL`dependsonthelocationofthedatabasedatabaseURL:"https://DATABASE_NAME.firebaseio.com",};//InitializeFirebasefirebase.initializeApp(firebaseConfig);//InitializeRealtimeDatabaseandgetareferencetotheserviceconstdatabase=firebase.database();

You're ready to start using theFirebase Realtime Database!

Next Steps

• Learn how tostructure data forRealtime Database.

• Scale your data across multiple databaseinstances.

• Read and write data.

• View your database in theFirebase console.

• Prepare to launch your app:

  • EnableApp Check to help ensure that only yourapps can access your databases.

  • Set upbudgetalertsfor your project in theGoogle Cloud console.

  • Monitor theUsage and billingdashboard in theFirebase console to get an overall picture of your project'susage across multiple Firebase services.You can also visit theRealtime DatabaseUsagedashboard for moredetailed usage information.

  • Review theFirebase launch checklist.