Firebase Authentication Pricing: MAU and SMS Costs

For Firebase Authentication with Identity Platform on the Blaze plan, most email, social, anonymous, and custom-provider usage is priced by monthly active users (MAU) after the included tier. A user is active when the account is used during the billing month; an inactive account can remain stored without becoming a billable MAU.

Forecast MAU from users who actually sign in during a month, not total registrations. Keep consumer providers separate from SAML and OpenID Connect because enterprise providers have a different included tier and rate. Confirm current thresholds on the official Identity Platform pricing page before approving a budget.

Phone authentication and SMS multi-factor authentication are billed per message sent, and the price varies by destination region. Estimate attempted messages rather than successful verifications: retries, delivery failures, test traffic, and abuse can all increase sent SMS without increasing active users.

Create a country-level forecast using monthly sign-in attempts, the share that requires SMS, and average messages per completed verification. Restrict SMS regions to markets you serve, monitor sent-versus-verified metrics, rate-limit retry flows, and use test phone numbers during development.

Base Firebase Authentication and Firebase Authentication with Identity Platform do not have identical pricing and limits. The optional Identity Platform upgrade enables features such as MFA, SAML, OIDC, multi-tenancy, blocking functions, enhanced logging, and an SLA, but it also introduces plan-specific active-user limits and MAU billing rules.

Record whether the project is on Spark or Blaze and whether Identity Platform is enabled. Then review Authentication usage, Identity Platform billing, and sent SMS metrics each month. Add the resulting auth estimate to the calculator's broader database, compute, storage, and egress scenario instead of treating login as the application's whole backend cost.