Firebase Auth is dramatically cheaper at scale. Auth0 wins on enterprise features. Here's the full cost and feature breakdown to help you choose.
Auth0 Wins When
Firebase Auth Wins When
| Scale | Auth0 Essentials | Auth0 (Annual) | Firebase Auth | Firebase (Annual) | Savings w/ Firebase |
|---|---|---|---|---|---|
| 1,000 MAU | $55 | $660 | Free | $0 | 🔥 Firebase is free |
| 5,000 MAU | $135 | $1,620 | Free | $0 | 🔥 Firebase is free |
| 10,000 MAU | $235 | $2,820 | Free | $0 | 🔥 Firebase is free |
| 25,000 MAU | $535 | $6,420 | Free | $0 | 🔥 Firebase is free |
| 50,000 MAU | $1,035 | $12,420 | Free | $0 | 🔥 Firebase is free |
| 75,000 MAU | $1,535 | $18,420 | $138 | $1,650 | Save ~$16,770/yr |
| 100,000 MAU | $2,035 | $24,420 | $275 | $3,300 | Save ~$21,120/yr |
| 500,000 MAU | Custom | $80K+ | $2,475 | $29,700 | Save ~$-29,620/yr |
Auth0 Essentials estimates. Firebase Auth free to 50K MAU, then $0.0055/MAU. Firebase requires Blaze plan for phone auth.
| Feature | Auth0 | Firebase Auth |
|---|---|---|
| Free tier | 7,500 MAU | 50,000 MAU |
| Cost at 50K MAU | $1,035/mo | Free |
| Cost at 100K MAU | $2,035/mo | $275/mo |
| RBAC / Roles | ✓ Built-in | ✗ Manual via Firestore |
| Enterprise SSO (SAML) | ✓ B2B plans | ✗ Not native |
| SCIM provisioning | ✓ Enterprise | ✗ No |
| Machine-to-Machine tokens | ✓ Professional+ | ✗ No |
| Custom login UI | ✓ Universal Login | ✓ FirebaseUI |
| Social login | ✓ 30+ providers | ✓ Google/FB/Apple etc |
| MFA (TOTP, SMS) | ✓ All plans | ✓ Free plan |
| Advanced attack protection | ✓ Professional+ | ✗ Basic only |
| 99.99% SLA | ✓ Enterprise | ✗ Standard SLA |
| HIPAA BAA | ✓ Enterprise | ✗ Not available |
| Actions / Extensions | ✓ Full pipeline | ✗ Limited |
| Firebase ecosystem | ✗ No | ✓ Firestore, Hosting, Functions |
| React/Next.js SDK | ✓ Excellent | ✓ Good |
| Multi-tenant (Organizations) | ✓ B2B plans | ✗ Manual only |
Considering migrating from Auth0 to Firebase?
Migration involves re-hashing passwords (Auth0 uses bcrypt; Firebase uses scrypt), updating SDKs, and managing a cutover window. Expect 2–8 weeks of engineering for a full migration. Consider the savings vs engineering cost for your specific MAU level. Firebase pricing guide →