By Mehdi HassanClerk vs Auth JS vs Supabase Auth vs WorkOS: which should a SaaS startup use?
Most early SaaS startups on Next.js should use Clerk if they want to ship fast with good-looking sign-in screens, or Supabase Auth if they already use Supabase. Choose Auth.js for full control and no per-user bill. Choose WorkOS, alone or alongside another option, when enterprise buyers start asking for single sign-on.
Auth looks like a solved problem until you sell to companies. Then you need teams, roles, invites, domain capture and SSO. This comparison is part of our hub on full-stack product engineering for startups and looks at both the engineering and the user experience of each option.
Clerk | Auth.js | Supabase Auth | WorkOS | |
|---|---|---|---|---|
Model | Hosted service | Open-source library | Part of Supabase | Hosted service |
Prebuilt sign-in UI | Yes, polished components | Minimal; you build it | Basic; mostly you build it | Yes, hosted AuthKit |
Organizations and roles | Built in | Build yourself | Build yourself | Built in |
SAML SSO | Available; check plan | Not built in | Available; check plan | Core strength |
Directory sync (SCIM) | Check current plans | No | No | Yes |
Where user data lives | Clerk | Your database | Your Supabase Postgres | WorkOS |
Lock-in | Medium | Low | Low to medium | Medium |
Features and plans change often in this category, so confirm SSO and directory sync availability on each vendor's current pricing page.
What does the sign-in UX look like with each option?
The sign-in experience differs more than most teams expect. Clerk and WorkOS give you finished, tested screens for sign-in, sign-up, password reset, multi-factor and account management. Auth.js and Supabase Auth give you the logic, and your team designs and builds the screens, which means more work and full control over the brand.
- Clerk: drop-in components for sign-in, user menus, profile pages and organization switching. You theme them; you don't redesign them from scratch.
- WorkOS AuthKit: a hosted, customizable sign-in flow that routes users to their company's identity provider when SSO applies.
- Auth.js: every screen is yours, including error states, email verification and account linking. Expect real design and build time.
- Supabase Auth: helpers and starter components, but most production teams design their own flows.
When is Clerk the right choice?
Clerk is the right choice when speed matters more than control: an early-stage SaaS on Next.js that needs sign-in, organizations, invites and roles working this week. Its Next.js integration is mature, and its organization features cover a lot of B2B needs without custom code.
Pros
- Fastest route to production-grade sign-in and account screens
- Organizations, invites and roles out of the box
- Multi-factor, social login and session management handled for you
Cons
- Per-user pricing grows with your user base
- User data lives with a vendor, which some buyers will ask about
- Migrating away means exporting users and rebuilding screens
When is Auth.js the right choice?
Auth.js, formerly NextAuth.js, is the right choice when you want auth inside your own codebase and database, with no per-user fees and no vendor holding your users. It handles OAuth providers, email links and sessions, and stores data through adapters for your database.
The trade-off is everything around sign-in: organizations, invitations, roles, admin tools and SSO are yours to build. Also check the project's status before you commit. Auth.js is now maintained by the Better Auth team, which points new projects toward Better Auth, so read the current documentation and weigh that path too.
What you build yourself with a library-based auth
With Auth.js or a similar library, plan for these pieces in your backlog: an organizations table and membership model, invitation emails and acceptance flows, role checks in your data-access layer, account settings screens, session and device management, and an admin view for support.
None is hard alone, but together they're a real chunk of work. Our guide to building a SaaS app with Next.js explains why the membership model should exist from day one, even if every user has one workspace today.
When is Supabase Auth the right choice?
Supabase Auth is the right choice when your database is Supabase. Users live in your Postgres project, and the signed-in user's identity is available inside row-level security policies, so the database itself can enforce who sees what. That's a strong safety property for multi-tenant SaaS.
You'll build your own organization model and most of the UI. If you're still choosing a backend, our comparison of Supabase vs Firebase vs custom Postgres covers how the auth choice affects your exit costs.
When do you need WorkOS and enterprise SSO?
You need WorkOS, or an equivalent, when enterprise prospects require SAML single sign-on, SCIM user provisioning or audit logs before they'll sign. Those requirements often appear in security questionnaires, and they can block a deal that's otherwise won.
WorkOS's admin portal lets a customer's IT team configure their own SSO connection, which saves your team from walking every customer through identity provider settings. Some startups start on Clerk or Supabase Auth and add WorkOS only for enterprise accounts. Others start on WorkOS from day one when the target market is clearly enterprise.
Which auth option should you pick at each stage?
Pick for the next twelve months, not for the next five years, but don't pick something that blocks your first enterprise deal. The most expensive mistake is a single-user auth model that has to be rebuilt when the first company asks for teams.
