# Firebase Authentication

**Provider:** Google Firebase
**Category:** auth
**Base URL:** `https://identitytoolkit.googleapis.com/v1`
**Auth:** api-key — `?key=AIzaSy...`
**Rate Limit:** 1M users per project (Spark)
**Free Tier:** Yes — [object Object]
**Pricing:** Free tier available (freemium)
**Docs:** https://firebase.google.com/docs/reference/rest/auth

## Description

Firebase Authentication provides backend services to authenticate users using passwords, phone numbers, and federated identity providers (Google, Facebook, Apple, GitHub, Twitter, Microsoft). Handles JWT token lifecycle, refresh tokens, and email verification flows.

## Endpoints

| Method | Endpoint | Description |
|--------|----------|-------------|
| POST | `https://identitytoolkit.googleapis.com/v1/accounts:signUp` | Create a new email/password user |
| POST | `https://identitytoolkit.googleapis.com/v1/accounts:signInWithPassword` | Sign in with email and password |
| POST | `https://identitytoolkit.googleapis.com/v1/accounts:sendOobCode` | Send password reset or verification email |
| POST | `https://identitytoolkit.googleapis.com/v1/accounts:update` | Update user profile or password |
| POST | `https://identitytoolkit.googleapis.com/v1/accounts:lookup` | Look up user data by ID token |
| POST | `https://identitytoolkit.googleapis.com/v1/token` | Refresh an ID token |

## Authentication

Include your Firebase Web API Key as a key query parameter for REST endpoints.

```
?key=AIzaSy...
```

## Sample Request

```bash
curl -X POST "https://identitytoolkit.googleapis.com/v1/accounts:signInWithPassword?key=$FIREBASE_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "email": "user@example.com",
    "password": "securepassword",
    "returnSecureToken": true
  }'
```

## Sample Response

```json
{
  "localId": "ZY6sY3NfRXYJ0N...",
  "email": "user@example.com",
  "displayName": "",
  "idToken": "eyJhbGciOiJSUzI1NiIsImtpZCI6...",
  "registered": true,
  "refreshToken": "APZUo0...",
  "expiresIn": "3600"
}
```

## Pricing Details

Free forever for email/social auth. Phone auth: 10K verifications/month free on Spark; $0.006 per verification on Blaze plan after threshold.

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*Source: [API Map](https://apimap.dev/apis/firebase-auth/) — CC BY 4.0*