Firebase Authentication
Firebase Authentication is Google's managed auth service, part of the Firebase platform Google acquired in October 2014; usage above the free tier now bills through Google Cloud Identity Platform. Client SDKs are Apache-2.0 (firebase JS SDK is at v12.16.0, July 2026) but the auth backend itself is a closed, unversioned Cloud service. It's free for the first 50,000 MAU across email/password, Google, Apple, GitHub, Microsoft, Yahoo and anonymous sign-in; SAML/OIDC federation is free only to 50 MAU. Classic phone/SMS sign-in has no free production tier (10 SMS/day free for testing only) and runs roughly $0.01-$0.06 per verification depending on country. Firebase also offers a separate, newer Phone Number Verification product (carrier-based, non-SMS, reached general availability May 2026) priced per-country and tiered by monthly volume, from about $0.029-$0.031 in Spain to $0.125-$0.135 in Indonesia — don't confuse the two when budgeting. Firebase's SDK is the dominant analytics/services SDK on Android, present in the large majority of apps on Google Play, and Google describes the platform as trusted by millions of apps and businesses. Current version/status: JS SDK v12.16.0 (Jul 2026); auth backend is an unversioned GCP SaaS. License: Proprietary SaaS (client SDKs Apache 2.0). Pricing: Free to 50,000 MAU for email/social/anonymous auth (SAML/OIDC free only to 50 MAU); graduated $0
Pick Firebase Auth when you're already running Firestore/Cloud Functions and want auth billed on the same Google invoice — 50,000 free MAU now just matches Clerk's free tier (Clerk raised its own limit from 10,000 to 50,000 monthly retained users in Feb 2026) but still undercuts Auth0's headline tier for that stack. Skip it if phone is your primary login: there's no free production tier for phone-based sign-in, and per-verification costs on Firebase's newer carrier-based verification product (up to ~$0.135 in Indonesia) can outrun what Auth0 or Clerk charge for equivalent volume. For Postgres-native apps, Supabase Auth beats Firebase's entry-level overage rate ($0.00325 vs $0.0055/MAU) and bundles row-level security for free. Known weakness: Google's own docs concede phone-based sign-in has no free production tier at all, and Firebase now runs two differently-priced phone products — classic SMS sign-in versus the newer carrier-based Phone Number Verification, whose per-verification pricing varies more than 4x by country — so the widely-quoted "50,000 free MAU" headline doesn't cover phone-based auth either way.
See how it ranks →