Authentication is the last thing you should build from scratch. Clerk, Auth0, Supabase Auth, NextAuth, and Lucia take different approaches to the same problem: getting users logged in securely without 100 hours of work. Here's the comparison.
Quick Comparison
| Clerk | Auth0 | Supabase Auth | NextAuth (Auth.js) | Lucia | |
|---|---|---|---|---|---|
| Type | Hosted + embeddable UI | Hosted (universal login) | Hosted (Supabase platform) | Library (bring your own DB) | Library (bring your own DB) |
| Best for | React/Next.js, best DX | Enterprise, multi-protocol | Supabase users, simplicity | Full control, open source | Session-based auth, full control |
| Free tier | 10K MAU, unlimited projects | 7.5K MAU (B2C), 500 (B2B) | 50K MAU | Free (open source) | Free (open source, unmaintained) |
| Social login | Google, GitHub, Apple, 20+ more | 40+ providers | Google, GitHub, Apple, 10+ | 50+ providers (configure yourself) | Manual (configure yourself) |
| Multi-tenancy | Excellent (organizations API) | Excellent (organizations) | No (single project) | No (you build it) | No (you build it) |
Clerk — The Developer Experience Gold Standard
Clerk provides drop-in React components (<SignIn />, <UserButton />) that look polished and handle the entire auth flow. The dashboard shows active users, sign-up sources, and suspicious activity. It's the fastest way to add auth to a Next.js app — literally 10 minutes from zero to working login.
Best for: React/Next.js developers, teams that want auth to Just Work, projects that need multi-tenancy (organizations), developers who value beautiful pre-built UI.
Pricing concern: Free tier is generous (10K MAU), but grows expensive at scale ($0.02/MAU beyond).
Auth0 — Enterprise-Grade, Maximum Flexibility
Auth0 (now part of Okta) is the most feature-complete auth platform. It supports every protocol (OAuth 2.0, OIDC, SAML, LDAP, WSFed), 40+ social providers, and has the most sophisticated security features (anomaly detection, brute force protection, breached password detection).
Best for: Enterprise applications, B2B SaaS with complex org structures, applications that need SAML/LDAP, regulated industries.
Pricing concern: Expensive at scale. B2B features (SSO, MFA policies) require Enterprise tier. Free tier is only 500 B2B MAU.
Supabase Auth — Simplest Option for Supabase Users
If you already use Supabase for your database, Supabase Auth is the simplest choice — it's already configured. Row-Level Security (RLS) policies tie directly to authenticated users. The free tier (50K MAU) is the most generous of any hosted solution.
Best for: Supabase users, side projects, solo developers, projects that want auth + database from one vendor.
NextAuth.js (Auth.js) — Full Control, No Vendor Lock-In
NextAuth (now Auth.js) is an open-source library that gives you complete control over your auth implementation. You own the user data, the session logic, and the database. It supports 50+ providers. The tradeoff: more code to write and maintain.
Best for: Developers who want full control, projects that can't use a hosted auth service, teams with specific compliance requirements.
Decision Matrix
| Scenario | Best Auth Solution |
|---|---|
| Next.js app, fastest to implement | Clerk |
| Enterprise, SAML/LDAP, B2B | Auth0 |
| Supabase stack, side project | Supabase Auth |
| Full control, open source, no vendor lock-in | NextAuth.js |
| Best free tier for scale (50K MAU) | Supabase Auth |
Bottom line: Clerk for Next.js apps — the best DX by far. Auth0 for enterprise. Supabase Auth if you already use Supabase. NextAuth for full control. Don't build auth from scratch — the security risks aren't worth it. See also: Backend Comparison and Web Security Basics.