TL;DR
Build and deploy a full-stack app in 2026 for $0 using Google AI Studio’s vibe coding experience, the Antigravity agent, and Firebase’s free tier. You can ship authentication, a real-time database, backend functions, and hosting without a credit card.
Introduction
Building a full-stack app traditionally meant combining multiple services: hosting, a database, authentication, and backend infrastructure. Even when each provider offered a free plan, managing limits across several platforms added complexity.
Google AI Studio’s vibe coding experience, launched on March 19, 2026, combines AI-assisted code generation with Firebase backends and hosting in one workflow. The free tier does not require a credit card.
In this guide, you will build a real-time multiplayer application with:
- Authentication
- A Firestore database
- Serverless backend logic
- Firebase Hosting
- A $0 deployment cost
💡 AI tools such as Google AI Studio can accelerate code generation, but API development still needs testing and documentation. Apidog provides free tools to design, mock, test, and document APIs before implementation. Define your API schema, generate mocks for frontend work, and validate AI-generated backend behavior against the specification.
The 2026 Free Stack
Before building, verify which limits apply to each service.
| Service | Free tier limits | What you get |
|---|---|---|
| Google AI Studio | 60 requests/min, 1M tokens/day | Vibe coding experience and Antigravity agent access |
| Firebase Authentication | 10K monthly active users | Email/password, Google, and GitHub sign-in |
| Cloud Firestore | 1GB storage, 50K reads/day | Real-time database |
| Firebase Hosting | 10GB storage, 360MB/day transfer | CDN hosting for frontend apps |
| Cloud Functions | 2M invocations/month | Serverless backend logic |
| Antigravity Agent | Included with AI Studio free tier | Persistent builds and multi-step edits |
What You Can Build Within the Free Tier
For a side project or MVP, the free tier can support:
- Up to 10,000 monthly active users
- Up to 1GB of user and application data
- Millions of Firestore reads
- Frontend hosting within Firebase Hosting transfer limits
- Up to 2 million backend function invocations per month
When You May Need to Pay
Expect to upgrade when:
- You exceed 10K monthly active users.
- Your Firestore database grows beyond 1GB.
- You need Firebase features that require billing.
- Your AI Studio usage exceeds daily limits.
For many MVPs, learning projects, and portfolio apps, the free tier can remain sufficient for months or years.
Step 1: Create a Google AI Studio Account
Create an account before generating your app.
- Go to
aistudio.google.com. - Select Sign in with Google.
- Sign in with a Gmail account.
- Accept the terms of service.
- Open the Projects dashboard.
Time: about 2 minutes
Cost: $0
Step 2: Start a Vibe Coding Session
Your initial prompt should explicitly constrain the generated app to Firebase’s free tier.
Prompt Template
Build a [type of app] that [core functionality].
Requirements:
- Must work on Firebase free tier (Spark Plan)
- No paid APIs or services
- Use free authentication (email/password or Google sign-in)
- Keep database under 1GB
Features:
- Feature 1
- Feature 2
- Feature 3
UI:
- Use shadcn/ui components
- Mobile-responsive
- Dark mode
Example: Multiplayer Trivia App
Use this prompt to generate a real-time multiplayer trivia game:
Build a real-time multiplayer trivia game that works entirely on Firebase free tier.
Requirements:
- Must work on Firebase Spark Plan (no paid services)
- Free authentication only (Google sign-in)
- Keep database schema under 1GB
- Use Cloud Functions free tier (2M invocations/month)
Features:
- 2-4 players per game room
- Real-time question sync
- Score tracking and leaderboard
- 30-second timer per question
- 100+ trivia questions included
UI:
- shadcn/ui components
- Mobile-responsive
- Dark mode with purple accents
- Framer Motion for transitions
Review What the Agent Generates
The Antigravity agent can generate and configure:
- Frontend: React, TypeScript, and shadcn/ui
- Backend: Firebase Cloud Functions
- Database: Firestore collections and security rules
- Authentication: Google sign-in integration
- Hosting: Firebase Hosting configuration
Before deploying, inspect generated configuration files, Firestore security rules, and any Cloud Function code. Confirm that no generated service requires a paid Firebase plan.
Step 3: Deploy to Firebase Hosting
Deploy from the vibe coding interface after reviewing the generated application.
Use the Free Firebase Subdomain
Firebase Hosting provides a free deployment URL:
your-app.web.app
A custom domain requires purchasing the domain separately and may require adding billing to your Firebase project.
For prototypes, portfolio projects, and early MVPs, use the default .web.app domain.
Step 4: Add Free External APIs
External APIs can provide app data without adding paid infrastructure.
| API | Free tier | Use case |
|---|---|---|
| Open Trivia Database | Unlimited | Trivia questions |
| The Cat API | Unlimited | Random cat images |
| JSONPlaceholder | Unlimited | Fake data for testing |
| PokeAPI | Unlimited | Pokémon data |
| OpenWeatherMap | 1K calls/day | Weather data |
Example: Add Open Trivia Database
Prompt the agent with:
Add integration with the Open Trivia Database API (opentdb.com) to fetch unlimited free trivia questions. Cache questions in Firestore to reduce API calls.
The generated service can look like this:
// src/services/triviaApi.ts
const API_BASE = 'https://opentdb.com/api.php';
export async function fetchTriviaQuestions(
amount: number = 10,
category?: string
) {
const params = new URLSearchParams({
amount: amount.toString(),
type: 'multiple',
});
if (category) {
params.append('category', category);
}
const response = await fetch(`${API_BASE}?${params}`);
const data = await response.json();
return data.results.map((q: any) => ({
question: q.question,
options: [...q.incorrect_answers, q.correct_answer].sort(),
correctAnswer: q.correct_answer,
category: q.category,
}));
}
For production code, add error handling before using the response:
if (!response.ok) {
throw new Error(`Trivia API request failed: ${response.status}`);
}
Free Authentication Options
| Provider | Free tier | Setup complexity |
|---|---|---|
| Firebase Auth (Email) | Unlimited | Easy |
| Firebase Auth (Google) | Unlimited | Easy |
| Firebase Auth (GitHub) | Unlimited | Easy |
| Firebase Auth (Anonymous) | Unlimited | Easiest |
Avoid paid authentication providers when your goal is to stay within a $0 stack.
Use Apidog’s free tier to validate AI-generated API structures. Import your generated Firestore-backed API design, create mock endpoints for Cloud Functions, and test the frontend against realistic responses before deployment. See the complete API mocking guide for examples.
Step 5: Monitor Free Tier Usage
Monitor usage before your app reaches a limit.
Check Firebase Usage
- Open
console.firebase.google.com. - Select your Firebase project.
- Click Usage in the left sidebar.
- Review Spark Plan metrics.
Key Metrics
| Metric | Free limit | Suggested alert threshold |
|---|---|---|
| Firestore storage | 1GB | 800MB |
| Firestore reads/day | 50K | 40K |
| Firestore writes/day | 20K | 16K |
| Functions invocations/month | 2M | 1.6M |
| Hosting transfer/day | 360MB | 300MB |
| Auth users | 10K/month | 8K |
Optimize Before You Hit Limits
If Firestore reads are high:
- Add client-side caching.
- Batch read operations.
- Query only the records your UI needs.
- Add query limits.
// Avoid: reads the entire collection
const snapshot = await getDocs(collection(db, 'messages'));
// Prefer: reads a bounded result set
const snapshot = await getDocs(
query(collection(db, 'messages'), limit(20))
);
If function invocations are high:
- Consolidate related function logic.
- Cache reusable results in Firestore.
- Use scheduled functions instead of unnecessary triggers.
If hosting transfer is high:
- Compress images.
- Use CDN caching.
- Lazy-load large components and assets.
Real Apps You Can Build on Free Tiers
1. Multiplayer Trivia Game
- Users: Up to 10K monthly
- Database: Questions and player data, around 200MB
- Functions: Game logic and score updates
- Cost: $0
2. Habit Tracking App
- Users: Up to 10K monthly
- Database: User habits and streaks, around 500MB
- Functions: Daily reminders and streak calculations
- Cost: $0
3. Real-Time Chat App
- Users: Up to 5K concurrent users with stored message history
- Database: Messages and user profiles, around 800MB
- Functions: Message routing and notifications
- Cost: $0
4. Collaborative Whiteboard
- Users: Up to 3K monthly active users
- Database: Board state and drawings, around 600MB
- Functions: Real-time sync and export
- Cost: $0
Common Free Tier Pitfalls
Pitfall 1: Accidentally Enabling Paid Firebase Features
Problem: Firebase may prompt you to add billing for some features.
Solution: Stay on the Spark Plan and avoid:
- Custom domain hosting when billing is required
- Cloud Run
- Using the Emulator Suite as a production service
If Firebase displays a billing prompt, select Maybe Later unless you intentionally want to upgrade.
Pitfall 2: AI Studio Rate Limits
Problem: The free tier is limited to 60 requests per minute and 1M tokens per day.
Solution:
- Work in focused sessions.
- Use follow-up prompts instead of restarting the conversation.
- Export generated code locally after completing a feature.
Pitfall 3: Expensive Firestore Queries
Problem: Reading entire collections can consume daily reads quickly.
Solution: Use indexed, filtered, and limited queries.
const recentMessagesQuery = query(
collection(db, 'messages'),
orderBy('createdAt', 'desc'),
limit(20)
);
const snapshot = await getDocs(recentMessagesQuery);
Pitfall 4: Function Cold Starts
Problem: Free Cloud Functions can have cold-start delays of roughly 1–2 seconds.
Solution:
- Keep functions small and focused.
- Use a minimum timeout of 60 seconds.
- Move simple, non-sensitive logic to the client when appropriate.
Where Apidog Fits
Google AI Studio helps generate the application. Apidog helps verify API behavior.
Free Apidog Features
- API design with a visual editor
- Mock server generation
- Automated test scenarios
- Team collaboration for up to three members
Suggested Workflow
- Design the API schema in Apidog.
- Generate application code with Google AI Studio.
- Test the frontend against Apidog mocks.
- Implement and validate Cloud Functions.
- Deploy to Firebase.
See How to Test REST APIs for the complete workflow.
When to Upgrade
Stay Free When You Are
- Building a side project
- Validating an MVP
- Learning full-stack development
- Creating portfolio projects
- Testing an idea before committing budget
Upgrade When
- Revenue justifies infrastructure costs.
- Users consistently exceed free-tier limits.
- You need custom domains.
- You need advanced monitoring.
- Your team needs paid collaboration features.
Smart Upgrade Path
- Start free: Build and launch using free tiers.
- Validate: Collect real user feedback.
- Monetize: Add a revenue stream.
- Upgrade: Use revenue to fund infrastructure.
Avoid paying for infrastructure before you have evidence that users will pay for the product.
Conclusion
A $0 full-stack app is practical in 2026. Google AI Studio, Antigravity, Firebase Authentication, Firestore, Cloud Functions, and Firebase Hosting provide enough infrastructure to build and launch many MVPs.
For $0, you can get:
- AI-powered code generation
- Authentication for up to 10K monthly users
- 1GB of database storage
- CDN hosting
- Up to 2M serverless function invocations per month
- Real-time application capabilities
To start, you need:
- A Google account
- An app idea
- A plan for staying within free-tier limits
Next Steps
- Sign up at
aistudio.google.com. - Enable Firebase Spark Plan.
- Start a vibe coding session with the prompt template.
- Review generated code and Firestore rules.
- Deploy to Firebase Hosting.
- Use Apidog’s free tier to test and document your APIs.
FAQ
Is Google AI Studio completely free?
Google AI Studio offers a free tier with 60 requests per minute and 1 million tokens per day. This is sufficient for building multiple full-stack apps. Paid tiers start at $20/month for higher limits.
Does Firebase free tier really last forever?
Yes. Firebase Spark Plan has no expiration. You stay on the free tier as long as you remain within usage limits. Many apps run on Spark Plan for years before requiring upgrades.
Can I monetize apps built on free tiers?
Yes. You keep your revenue. Free tiers are designed to help developers build and launch, while providers benefit when successful applications eventually need paid capacity.
What happens if I exceed free limits?
Firebase will not automatically charge you. You may:
- Be throttled until the next billing cycle
- Receive a prompt to add billing
- Need to optimize usage or manually upgrade
Do I need a credit card to start?
No. Google AI Studio and Firebase Spark Plan work without billing information. Add a card only if you choose to upgrade.
Can I use custom domains on the free tier?
Firebase Hosting includes a .web.app subdomain. Custom domains require purchasing the domain separately and may require adding billing.
What is the catch?
There is no trial expiration for the Firebase Spark Plan. Google offers free tiers to build developer loyalty, grow the Firebase ecosystem, and support future customers that need paid capacity.
How long does it take to build a real app?
With vibe coding, an MVP can take 1–2 hours. Traditional development can take 2–4 weeks. AI handles much of the boilerplate, while you focus on product requirements and validation.
Can I export the code and self-host it?
Yes. Export projects as ZIP files or push them to GitHub. You can host the generated code on Vercel, Netlify, your own server, or another provider.
Is generated code production-ready?
The agent can generate working code that follows common patterns, but you should always:
- Review generated code
- Test thoroughly
- Add app-specific error handling
- Review security rules
- Run security audits before handling sensitive data
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