Auth0 bills by Monthly Active Users — and the cost curve is steep. Understanding how MAU tiers work is essential before you scale beyond a few thousand users.
What counts as an MAU
Any unique user who completes an authentication event (login, token refresh, passwordless) at least once in a calendar month.
What doesn't count
Registered users who don't log in. You can have 1 million registered users — only those who authenticate in a given month count toward your MAU.
Multi-login counting
A user logging in 100 times in one month counts as 1 MAU. The metric rewards high-engagement, low-unique-user apps.
Monthly reset
MAU resets at the start of each calendar month. A user active in January and February counts as 2 MAU across 2 months.
The Core Problem
Auth0's pricing tiers are not linear. As you grow, each additional user becomes more expensive because you're bumped into a higher-priced bracket. The marginal cost per MAU actually increases at intermediate tiers, unlike competitors like AWS Cognito which charge a flat $0.0055/MAU regardless of scale.
| MAU | Essentials /mo | Professional /mo | Firebase Auth /mo | AWS Cognito /mo | Auth0 vs Firebase |
|---|---|---|---|---|---|
| 500 MAU | $35 | — | Free | Free | ∞ more |
| 1K MAU | $55 | $240 | Free | Free | ∞ more |
| 5K MAU | $135 | $360 | Free | Free | ∞ more |
| 10K MAU | $235 | $520 | Free | Free | ∞ more |
| 25K MAU | $535 | $895 | Free | Free | ∞ more |
| 50K MAU | $1,035 | $1,645 | Free | Free | ∞ more |
| 100K MAU | $2,035 | $3,145 | $275 | $275 | 7x more |
Firebase Auth free to 50K MAU (Spark plan). Cognito free to 50K MAU. Auth0 Essentials estimated from published tier pricing.
Auth0 Essentials starts at $35/month for 500 MAU. Each additional 100 MAU block above 500 adds approximately $4–$6. But at the boundary between Essentials and Professional, cost jumps dramatically.
Remove inactive users
Users who haven't logged in for 6+ months are unlikely to be active. Cleaning your user database reduces registered user count and future MAU potential. Use the Auth0 Management API to bulk-delete old accounts.
Extend session lifetimes
Longer session tokens mean fewer authentication events. If a user can stay logged in for 30 days without re-authenticating, they count as 1 MAU per month instead of potentially triggering new auth events.
Consolidate multiple tenants
MAU is counted per-tenant. If you run dev, staging, and prod as separate Auth0 tenants (each billed separately), consolidating staging into dev saves one plan. Use Auth0 environments feature where available.
Just-in-time user provisioning
Instead of pre-registering all users (e.g. employees in bulk), provision users only when they first log in. This avoids registering users who may never actually log in.
Evaluate the MAU-to-feature ratio
At 100K+ MAU, Auth0 becomes very expensive. Evaluate whether Auth0's enterprise features (RBAC, M2M, advanced MFA) are actually being used and worth the premium over Firebase Auth or Cognito.
At 25K+ MAU, seriously evaluate alternatives
Beyond 25,000 MAU, Auth0 Essentials costs $535+/month. Firebase Auth at this scale is free. AWS Cognito charges $0. If you don't need Auth0's enterprise features (RBAC, SAML, M2M), migrating to a cheaper provider could save $5,000–$20,000/year. See full alternatives comparison →
Enter your expected MAU and see Auth0 costs vs Firebase, Cognito, and Clerk — side by side.