Firebase Cheat Sheet

Updated 2026-04-29

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Firebase is Google's comprehensive backend-as-a-service (BaaS) platform that provides cloud infrastructure, databases, authentication, hosting, serverless functions, AI capabilities, and analytics for mobile and web applications. Firebase eliminates the need to build and manage backend infrastructure from scratch, offering real-time synchronization, automatic scaling, and deep integration with Google Cloud. In 2026, the platform has significantly expanded with Firebase App Hosting for full-stack web apps, Firebase AI Logic for client-side Gemini API access, Firebase SQL Connect (formerly Data Connect) for PostgreSQL integration, and Firestore pipeline queries with full-text and geospatial search — making it a comprehensive platform for both traditional and AI-powered applications.

What This Cheat Sheet Covers

This topic spans 26 focused tables and 237 indexed concepts, 121 flashcards. Below is a complete table-by-table outline of this topic, spanning foundational concepts through advanced details.

Table 1: Project Setup and ConfigurationTable 2: Firebase Authentication MethodsTable 3: Firestore Database OperationsTable 4: Firestore Security RulesTable 5: Firebase Cloud Functions TriggersTable 6: Firebase HostingTable 7: Firebase App HostingTable 8: Firebase StorageTable 9: Firebase SQL Connect (formerly Data Connect)Table 10: Firebase Cloud Messaging (FCM)Table 11: Remote ConfigTable 12: Firebase ExtensionsTable 13: Realtime Database OperationsTable 14: Firebase AnalyticsTable 15: Firebase Performance MonitoringTable 16: Firebase CrashlyticsTable 17: Firebase App DistributionTable 18: Firebase Test LabTable 19: Firebase ML KitTable 20: Firebase AI LogicTable 21: Firebase GenkitTable 22: Pricing PlansTable 23: Firebase CLI CommandsTable 24: Firestore Best PracticesTable 25: Firebase Security Best PracticesTable 26: Firebase Dynamic Links (Legacy)

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Table 1: Project Setup and Configuration

Before any Firebase feature works, you have to wire up a project — and that means two distinct setups. The client SDK (initializeApp(config)) runs in browsers and apps under security rules, while the Admin SDK runs on your server with elevated privileges that bypass those rules. The CLI commands and local emulators here are what you use day to day to deploy, switch between dev and production, and develop offline without touching live data.

Method	Example	Description
Initialize Firebase project (CLI)	`firebase init`	• Sets up a new Firebase project in the current directory • prompts to select services (Hosting, App Hosting, Functions, Firestore, etc.) and links to a Firebase project.
Deploy to Firebase	`firebase deploy`	• Deploys all configured services to production • supports partial deployment with `--only` flag (e.g., `--only hosting,functions`).
Initialize SDK (JavaScript)	`import { initializeApp } from 'firebase/app';` `const app = initializeApp(config);`	• Initializes Firebase SDK with project configuration (API key, project ID, app ID) • must be called before using any Firebase services.
Initialize Admin SDK (Node.js)	`const admin = require('firebase-admin');` `admin.initializeApp();`	• Initializes Firebase Admin SDK for server-side operations • bypasses security rules and provides elevated privileges for backend tasks.
Configure service account	`admin.initializeApp({` `credential: admin.credential.cert(key),` `});`	• Authenticates Admin SDK using a service account JSON key • required for server environments without default Application Default Credentials.
Local emulator setup	`firebase emulators:start`	• Starts local emulators for Auth, Firestore, Functions, Storage, Hosting, and App Hosting • enables offline development without touching production data.
Project alias management	`firebase use production`	Switches between project aliases (dev, staging, production) to prevent accidental deployment to wrong environment.
Automatic SDK initialization (App Hosting)	`initializeApp()`	• App Hosting auto-injects Firebase config, no arguments needed • prevents staging apps from accidentally accessing production data.
Admin Dart SDK (experimental)	`import 'package:dart_firebase_admin/dart_firebase_admin.dart';`	• Server-side Firebase operations in Dart for Flutter full-stack apps • supports Auth, Firestore, Messaging, Storage, and Security Rules.

Table 2: Firebase Authentication Methods

Firebase Auth handles the entire identity story so you don't build login from scratch. These rows span every way a user can prove who they are — email/password, the OAuth providers (Google, Apple, Facebook), passwordless email links, and phone or anonymous sign-in — plus the second-factor options (TOTP and SMS MFA) and the housekeeping functions for email verification, password resets, and signing out.

Provider	Example	Description
Email/password sign-up	`createUserWithEmailAndPassword(auth, email, password)`	• Creates a new user account with email and password credentials • automatically signs in the user after successful registration.

The rest of this section is part of the full cheat sheet

Table 3: Firestore Database Operations

Firestore is Firebase's flagship NoSQL document database, and this is the working vocabulary for it — creating, reading, updating, and deleting documents, then querying and paginating collections. A few rows highlight what makes Firestore distinctive: real-time onSnapshot listeners that fire on every change, atomic batches and transactions, collection-group queries across nested subcollections, and vector search for AI-powered nearest-neighbor lookups.

Operation	Example	Description
Add document (auto ID)	`addDoc(collection(db, 'users'), data)`	• Creates a new document with auto-generated ID • returns a `DocumentReference` with the new document's ID.

The rest of this section is part of the full cheat sheet

Table 4: Firestore Security Rules

Because Firestore is queried directly from untrusted clients, security rules are what actually protect your data — not your app code. These patterns are the everyday building blocks: requiring authentication, checking that a user owns a document, reading custom claims for role-based access, and validating incoming data types and fields. The last row is a warning as much as an example: allow read, write: if true opens everything and must never reach production.

Rule	Example	Description
Require authentication	`allow read, write: if request.auth != null;`	• Restricts access to authenticated users only • most common basic security rule.

The rest of this section is part of the full cheat sheet

Table 1: Project Setup and Configuration

Method	Example	Description
Initialize Firebase project (CLI)	`firebase init`	• Sets up a new Firebase project in the current directory • prompts to select services (Hosting, App Hosting, Functions, Firestore, etc.) and links to a Firebase project.
Deploy to Firebase	`firebase deploy`	• Deploys all configured services to production • supports partial deployment with `--only` flag (e.g., `--only hosting,functions`).
Initialize SDK (JavaScript)	`import { initializeApp } from 'firebase/app';` `const app = initializeApp(config);`	• Initializes Firebase SDK with project configuration (API key, project ID, app ID) • must be called before using any Firebase services.
Initialize Admin SDK (Node.js)	`const admin = require('firebase-admin');` `admin.initializeApp();`	• Initializes Firebase Admin SDK for server-side operations • bypasses security rules and provides elevated privileges for backend tasks.
Configure service account	`admin.initializeApp({` `credential: admin.credential.cert(key),` `});`	• Authenticates Admin SDK using a service account JSON key • required for server environments without default Application Default Credentials.
Local emulator setup	`firebase emulators:start`	• Starts local emulators for Auth, Firestore, Functions, Storage, Hosting, and App Hosting • enables offline development without touching production data.
Project alias management	`firebase use production`	Switches between project aliases (dev, staging, production) to prevent accidental deployment to wrong environment.
Automatic SDK initialization (App Hosting)	`initializeApp()`	• App Hosting auto-injects Firebase config, no arguments needed • prevents staging apps from accidentally accessing production data.
Admin Dart SDK (experimental)	`import 'package:dart_firebase_admin/dart_firebase_admin.dart';`	• Server-side Firebase operations in Dart for Flutter full-stack apps • supports Auth, Firestore, Messaging, Storage, and Security Rules.

Table 2: Firebase Authentication Methods

Provider	Example	Description
Email/password sign-up	`createUserWithEmailAndPassword(auth, email, password)`	• Creates a new user account with email and password credentials • automatically signs in the user after successful registration.

Table 3: Firestore Database Operations

Operation	Example	Description
Add document (auto ID)	`addDoc(collection(db, 'users'), data)`	• Creates a new document with auto-generated ID • returns a `DocumentReference` with the new document's ID.

Table 4: Firestore Security Rules

Rule	Example	Description
Require authentication	`allow read, write: if request.auth != null;`	• Restricts access to authenticated users only • most common basic security rule.