Auth is identity plus session state
A real auth system handles signup, login, password reset, OAuth, sessions, token refresh, email verification, and account recovery.
Authentication and Identity Providers
Best Free Authentication & Identity Providers 2026
Authentication is not just a login form. A real auth provider manages sessions, OAuth, email verification, password reset, MFA, organizations, roles, and sometimes SSO. The free tier decision should match your product shape before you have thousands of users locked into one identity system.
Fast answer
Use Supabase Auth when Postgres/RLS is central.
Use Clerk when frontend auth UX matters most.
Use Logto when you want OIDC/RBAC across multiple apps.
Last Updated: 2026-05-22
What auth providers really handle
Authorization is a separate layer
Login only tells you who the user is. Authorization decides what they can read, edit, invite, bill, or administer.
MAU is not the only free-tier boundary
Email sending, custom domains, MFA, SSO, organizations, audit logs, and machine-to-machine tokens often matter more than headline MAU.
Auth creates sticky lock-in
Migrating users, passwords, OAuth providers, sessions, tenants, and permission rules is harder than moving ordinary tables.
Quick recommendations
Choose by product shape: Postgres app, frontend-first SaaS, general OIDC identity layer, or B2B SaaS feature bundle.
Best for Postgres apps
Supabase Auth
Best when auth, user tables, Row Level Security, and product data should live near the same Postgres backend.
Best Auth0-style open alternative
Logto Cloud
Good when you need OIDC, RBAC, multi-language SDKs, and a more general identity layer across multiple apps.
Best frontend-first auth UX
Clerk
Excellent when polished React/Next.js components, session management, organizations, and dashboard-driven setup matter most.
Best SaaS feature bundle
Kinde
Useful when auth, feature flags, auditability, and entry-level B2B SaaS features are part of the same product decision.
Free auth provider comparison table
Use the table for MAU and feature scanning. Then check email delivery, SSO, organization support, and export paths before committing your users.
| PROVIDER | FREE STORAGE | MONTHLY BANDWIDTH | SPECS / COMPUTE | CONNECTION LIMITS | KEY CONSTRAINTS | ACTION |
|---|---|---|---|---|---|---|
Supabase AuthPOSTGRES NATIVE | 50,000 MAU | Unlimited Row Relations | Direct PG schema integration, built-in Row Level Security (RLS) policies | High performance native endpoints | Strict daily built-in SMTP email limits; requires external SMTP binding for production | Go to Site ↗ |
Logto CloudOIDC / AUTH0 ALT | 50,000 MAU | Unlimited Social Logins | Enterprise-grade RBAC, widest language SDK support (.NET/Go/Android/Java) | High-density cloud proxy infrastructure | Custom Domain mapping is locked under premium add-ons for free cloud tier | Go to Site ↗ |
ClerkFRONTEND DEVOPS | 10,000 MAU | Unlimited session syncs | Pre-built optimized UI/UX React/Next.js component kits, default basic MFA | Edge replication routing | Hard limit at 10k MAU; pure headless backend integration overhead is higher | Go to Site ↗ |
KindeSAAS ARSENAL | 7,500 MAU | Unlimited Feature Flags | Includes built-in feature flagging, user auditing, and entry-level SAML SSO hooks | Global Identity Router | Lowest MAU quota headroom among top options; steep tier jumps post-limit | Go to Site ↗ |
How to choose an auth provider
Choose by product shape, not login form
A personal app, SaaS dashboard, B2B workspace, mobile app, and internal admin tool need different auth primitives.
Inspect organization and tenant model early
If users belong to teams, workspaces, or organizations, make sure the provider supports invitations, roles, tenant switching, and billing ownership.
Plan email deliverability
Magic links, verification emails, password resets, and invites depend on email. Production apps usually need custom SMTP or a transactional email provider.
Keep permission rules close to data
Authentication identifies users; data-level authorization still belongs near the database, API, or policy engine that protects records.
Auth traps to check
Login works, permissions leak
Many apps ship login before authorization is designed. That creates private data leaks, broken tenant isolation, and admin actions exposed to normal users.
SMTP limits break onboarding
Free built-in email can be enough for demos but not production launches. Invite flows and password reset reliability are part of auth quality.
SSO becomes expensive late
B2B products often discover SAML, SCIM, audit logs, and enterprise roles late. These features may be outside the free tier.
User migration is painful
Password hashes, OAuth identities, sessions, MFA factors, and organization memberships can be hard to export or recreate.
Recommended auth stack patterns
Supabase Auth + RLS + Postgres
A compact stack for SaaS MVPs where auth state, user records, and data permissions should be close together.
Clerk + Next.js + Neon
A frontend-first SaaS stack: Clerk handles polished auth UX, Neon handles relational data, and Next.js owns app routes.
Logto + API gateway + microservices
A better fit when multiple apps and services need a shared OIDC identity layer and central RBAC model.
Related guides and categories
Supabase Provider Guide
See how Supabase Auth fits with Postgres, Storage, Edge Functions, and Realtime in the same backend.
Email & SMS APIs
Auth systems rely on email and sometimes SMS for verification, invites, password reset, and MFA.
BaaS Platforms
Compare full backend platforms when auth should ship together with database, storage, realtime, and APIs.
Authentication FAQ
What does an auth provider actually do?+
It handles login, signup, sessions, password reset, OAuth, email verification, token refresh, and often MFA, organizations, roles, and audit logs. It does not automatically solve all data permissions.
Which free auth provider is best for a SaaS MVP?+
Supabase Auth is strong if you already use Supabase/Postgres. Clerk is strong for Next.js frontend UX. Logto is attractive for OIDC/RBAC and Auth0-style needs. Kinde is useful when feature flags and SaaS tooling are part of the auth decision.
Is MAU the most important auth limit?+
MAU matters, but email limits, custom domain, organizations, SSO, MFA, roles, audit logs, and machine-to-machine auth can become more important as the product matures.
Should I build auth myself?+
For most public apps, no. Build your authorization and product-specific permission model carefully, but let a provider handle password resets, OAuth, sessions, email verification, and security-sensitive flows unless you have a strong reason.
What should I check before choosing auth?+
Check MAU, social providers, custom domain, email delivery, organizations, roles, SSO, MFA, audit logs, user export, SDK quality, and how permissions integrate with your database or API.