Firebase Authentication API
Google Firebase's authentication service supporting email/password, phone, and social logins (Google, Apple, GitHub, etc.) with a backend Admin SDK for user management and token verification.
Score Breakdown
⚙ Agent Friendliness
🔒 Security
Firebase Admin SDK with service account for user management. Client SDK uses public API key (safe). SOC2, ISO27001. Phone auth, OAuth providers, email/password all supported. Rate limits on auth operations prevent brute force.
⚡ Reliability
Best When
You're already in the Firebase/GCP ecosystem and need simple multi-provider auth without enterprise features.
Avoid When
You need SAML SSO, complex RBAC, or want to avoid vendor lock-in with Google.
Use Cases
- • Adding multi-provider auth to mobile or web apps quickly
- • Verifying Firebase ID tokens on the backend via Admin SDK
- • Managing users programmatically (create, disable, delete) via Admin SDK
- • Custom token generation for server-side authentication flows
- • Linking multiple auth providers to a single user account
Not For
- • Enterprise SSO/SAML (use Auth0, WorkOS, or Okta instead)
- • Complex authorization/RBAC beyond basic user management
- • Teams avoiding Google/GCP dependency
Interface
Authentication
Admin SDK uses a service account JSON key or Application Default Credentials (ADC). Very agent-friendly once credentials are configured. Public REST API uses API keys.
Pricing
Email and social auth are free at any scale. Phone auth costs money. Requires upgrading to Blaze plan for many features even if usage stays low.
Agent Metadata
Known Gotchas
- ⚠ Admin SDK does not emit events/webhooks - agents can't react to auth events without custom triggers
- ⚠ ID token expiry is 1 hour - backend agents must handle token refresh or use Admin SDK directly
- ⚠ Service account JSON keys in code is a common security mistake - use ADC instead
- ⚠ Firebase Auth custom claims are limited to 1000 bytes total
- ⚠ Listing users requires pagination with cursor - large user bases require many API calls
- ⚠ No built-in audit logging for auth events without setting up Cloud Logging
Alternatives
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Scores are editorial opinions as of 2026-03-07.