Auth and identity · Comparison
Supabase Auth vs Firebase Auth vs Clerk vs Auth.js vs Auth0
Five common ways to add sign-in without building it from scratch. Two come bundled with a backend platform, two are dedicated hosted services, and one is a library that runs inside your own app. MAU means monthly active users.
5 options · 9 questions side by side · updated
| Compare | Supabase Auth | Firebase Auth | Clerk | Auth.js | Auth0 |
|---|---|---|---|---|---|
| What it is | Auth built into each Supabase project | Google's sign-in service for Firebase | Hosted auth with ready-made UI | Open-source library inside your app | Hosted identity platform from Okta |
| Where users live | A table in your own Postgres | Firebase's user store | Clerk's servers, synced by webhooks | Your database, through an adapter | Auth0's servers |
| Ready-made screens | A few UI blocks; mostly your own forms | FirebaseUI drop-in screens | Full sign-in, profile and team components | Basic default pages only | Hosted Universal Login page |
| Passkeys | Yes, recently added | Not built in | Yes, on paid plans | Experimental provider only | Yes |
| Enterprise SSO (SAML) | Pro plan and up, billed per SSO user | With the Identity Platform upgrade | One connection on Pro, more at extra cost | OIDC providers; SAML needs extra tools | Yes; one connection even on Free |
| Free allowance | 50,000 MAU | Unlimited email and social; 50,000 MAU with Identity Platform | 50,000 retained users per app | No limit; you host it | 25,000 MAU |
| First paid step | Pro, $25 a month | Blaze, pay as you go | Pro, $25 a month | None; you pay only for hosting | Essentials, from $35 a month |
| Lock-in | Low: standard Postgres you can export | High: tied to Firebase APIs | Medium: data exports, but UI to rebuild | Low: your code and your data | Medium: standard protocols, custom setup |
| Best for | Apps built on Supabase | Mobile apps built on Firebase | React and Next.js apps wanting finished UI | Existing apps that own their user data | B2B and enterprise requirements |
How to choose between Supabase Auth, Firebase Auth, Clerk, Auth.js and Auth0
- Pick Supabase Auth or Firebase Authentication when you already use that platform, since sign-in plugs straight into its data rules.
- Pick Clerk for finished sign-in, profile and team screens in React or Next.js with little code.
- Pick Auth.js for an existing app that keeps users in its own database; for new projects its maintainers point to Better Auth.
- Pick Auth0 when business customers need SAML single sign-on, directory sync and compliance paperwork.
The options
- Supabase AuthThe sign-in service built into every Supabase project, which keeps users in your own PostgreSQL database and issues tokens that row level security policies can check.
- Firebase AuthGoogle's hosted sign-in service for Firebase apps, with SDKs for Android, iOS, the web, Flutter and Unity that cover email, phone numbers and social accounts.
- ClerkA hosted sign-in and user management service with ready-made components, so a React or Next.js app gets sign-up, sign-in, profile and team screens in a few lines of code.
- Auth.jsAn open-source sign-in library for JavaScript apps, formerly NextAuth.js, that adds social login, email links and sessions to Next.js and other frameworks while keeping users in your own database.
- Auth0A hosted identity platform, owned by Okta, that runs sign-in for consumer and business apps, with enterprise features such as SAML single sign-on, fine-grained permissions and compliance certifications.
More comparisons
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- Express vs Fastify vs HonoThree JavaScript web frameworks with a similar feel. Express is the long-standing default, Fastify focuses on throughput and structure, and Hono is built on web standards so it can run almost anywhere.
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