Clerk

Clerk is authentication and user management delivered as drop-in components rather than as a protocol you implement. You install the SDK, mount a sign-in component, wrap the app in a provider, and you have sign-up, sign-in, MFA, password reset, session management and a user profile page that already look designed. For a small team that is days of work removed from the first sprint. The scope goes past login. It ships hosted UI components and headless hooks for when you want your own markup; social sign-in, email links, one-time codes, passkeys and passwords; multi-factor including TOTP and SMS; and — the feature that most often decides the purchase — Organizations, which gives you B2B tenancy with invitations, roles, permissions and org switching without designing that data model yourself. Session handling is JWT-based with short-lived tokens, and the framework integrations are unusually deep on Next.js, where middleware-level route protection is a few lines. Pricing is freemium and metered on retained users. Hobby is free. Pro is $25 a month, or $20 billed annually. Business is $300 a month, or $250 annually. Enterprise is custom. Paid plans include 50,000 monthly retained users, with additional users at about $0.02 each per month and volume discounts above that. The metric is worth reading carefully: Clerk counts a user as retained only if they come back at least 24 hours after signing up, so signup spikes and one-time visitors do not bill the way a raw monthly-active count would. The limitation to weigh is dependency. Authentication sits at the centre of your application, and Clerk holds the user records, so migrating away later is a real project rather than a config change — and pricing that is generous at 50,000 users is not free at a million. Self-hosting is not an option. Auth0 is the enterprise incumbent: more extensible, more expensive, and heavier to configure. Supabase Auth and Firebase Auth are effectively free with the rest of their platform and give you far less finished UI, which is the right trade if you are already on either. Auth.js (NextAuth) is free, open-source and self-hosted, and you own every screen and every edge case. WorkOS is the specialist when the requirement is enterprise SSO and SCIM for a handful of large customers rather than consumer signup. Choose Clerk when shipping the product matters more than owning the auth layer, and especially when you need B2B organisations early.