Auth & identity, in detail
Per-MAU pricing made auth the layer teams most regret outsourcing at scale — and the market answered with huge free tiers: a million MAUs at WorkOS, 50k retained users at Clerk, 25k at Auth0. The self-hosted and Google-subsidized options complete the picture.
| Tool | Free tier | Entry price | Billing unit | Watch out for | Best for |
|---|---|---|---|---|---|
| Clerk | 50,000 monthly retained users | Pro $25/mo + $0.02/user | Per retained user | Orgs/SAML are paid add-ons | Drop-in React/Next.js auth UI, fastest DX |
| WorkOS | AuthKit free to 1M MAUs | SSO $125/connection/mo | Per SSO connection | Costs concentrate in enterprise connections | Making a B2B SaaS enterprise-ready (SSO, SCIM) |
| Auth0 | 25,000 MAUs | Essentials $35/mo (500 MAU) | Per MAU tier | Steep cliffs between tiers; enterprise-gated features | Every protocol and IdP, compliance included |
| Supabase Auth | 50k MAU on free tier | Bundled with Pro $25/mo | Part of platform | Best when you're on Supabase anyway | Auth wired into Postgres row-level security |
| Keycloak | Unlimited — OSS | $0 + hosting | Your infra | Real ops burden: upgrades, HA, themes | Self-hosted escape from per-MAU pricing |
| Firebase Auth | Generous free (SMS billed) | Pay-as-you-go above | Per verification/SMS | Identity-Platform tier changes limits | Mobile-first auth subsidized by Google |
| Stytch | Free tier | Usage-based | Per MAU/API call | Smaller ecosystem than Auth0 | API-first auth: passkeys, magic links, fraud tools |
Pricing models and free tiers change often — check each vendor for current terms. Compiled July 2026; the most volatile figures verified on official pricing pages.
Official pages: Clerk · WorkOS · Auth0 · Supabase Auth · Keycloak · Firebase Auth · Stytch
Entry price at a glance
Cheapest paid plan, USD per month — per-user plans shown for a single seat. Hatched bars are usage-based or quote-only; values marked ~ are approximate.
Notes & recent changes
- Clerk bills 'monthly retained users' — users who return 24h+ after signup — which typically undercounts MAU-style billing meaningfully (verified Jul 2026).
- Auth0 raised its free tier from 7,500 to 25,000 MAUs in Sept 2024; the complaint isn't the free tier but the price cliffs above it.
- WorkOS AuthKit's 1M-free-MAU positioning is the category's most generous — its revenue comes from $125/connection enterprise SSO.
Which one should you pick?
- Next.js/React product → Clerk.
- B2B SaaS selling to enterprises → WorkOS.
- Compliance-heavy consumer scale → Auth0.
- Cost control at scale → Keycloak self-hosted (or Supabase Auth if it's your stack).