Firebase Authentication

Google-backed auth with generous free tier for mobile and web

Firebase Authentication provides backend services for user sign-in, supporting email/password, social providers (Google, Apple, Facebook, Twitter/X), phone SMS, and anonymous auth. Free for first 50,000 MAUs on email/password and social providers. Phone SMS auth billed per verification ($0.0075/SMS in US). SAML/OIDC enterprise SSO available at $0.015/MAU after 50 users.

Our take

Firebase Auth's 50,000 MAU free tier for email/password and social sign-in is genuinely generous — most consumer apps never hit it. The SDKs are excellent for mobile: the Flutter/Firebase pairing and native iOS/Android integrations are among the most polished auth implementations available. The hidden cost is phone SMS: once you enable phone number verification (common for consumer apps), costs appear immediately — $0.0075/SMS in the US, up to $0.34/SMS in some countries. High-SMS-volume apps (fintech, gig economy) can face significant unexpected bills. Auth0 handles enterprise SSO with more mature compliance controls; Clerk delivers better React/Next.js developer experience with pre-built components. Firebase Auth's sweet spot is mobile-first apps, especially those using Firestore or other Firebase products where the tight integration creates development speed advantages.

Product roadmap

Google is integrating Firebase Auth more deeply with Google Identity Platform and Cloud IAM for enterprise use cases. The Identity Platform (Firebase Auth's enterprise tier) adds SAML, multi-tenancy, and regulatory compliance features. Expect continued improvement in Flutter and multi-platform support as part of Google's mobile development platform strategy.